diff --git a/headless/chat/src/main/java/com/tencent/supersonic/headless/chat/knowledge/KnowledgeBaseService.java b/headless/chat/src/main/java/com/tencent/supersonic/headless/chat/knowledge/KnowledgeBaseService.java
index 7cf018360..4090c705b 100644
--- a/headless/chat/src/main/java/com/tencent/supersonic/headless/chat/knowledge/KnowledgeBaseService.java
+++ b/headless/chat/src/main/java/com/tencent/supersonic/headless/chat/knowledge/KnowledgeBaseService.java
@@ -8,43 +8,107 @@ import lombok.extern.slf4j.Slf4j;
 import org.springframework.stereotype.Service;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
 import java.util.stream.Collectors;
 
 @Service
 @Slf4j
 public class KnowledgeBaseService {
-    private static volatile Map<Long, List<DictWord>> dimValueAliasMap = new HashMap<>();
+    private static final Map<Long, List<DictWord>> dimValueAliasMap = new ConcurrentHashMap<>();
+    private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
 
+    /**
+     * Get dimension value alias map (read-only).
+     *
+     * @return unmodifiable view of the map
+     */
     public static Map<Long, List<DictWord>> getDimValueAlias() {
-        return dimValueAliasMap;
+        return Collections.unmodifiableMap(dimValueAliasMap);
     }
 
+    /**
+     * Add dimension value aliases with deduplication. Thread-safe implementation using
+     * ConcurrentHashMap.
+     *
+     * @param dimId dimension ID
+     * @param newWords new words to add
+     * @return updated list of aliases for the dimension
+     */
     public static List<DictWord> addDimValueAlias(Long dimId, List<DictWord> newWords) {
-        List<DictWord> dimValueAlias =
-                dimValueAliasMap.containsKey(dimId) ? dimValueAliasMap.get(dimId)
-                        : new ArrayList<>();
-        Set<String> wordSet =
-                dimValueAlias
-                        .stream().map(word -> String.format("%s_%s_%s",
-                                word.getNatureWithFrequency(), word.getWord(), word.getAlias()))
-                        .collect(Collectors.toSet());
-        for (DictWord dictWord : newWords) {
-            String key = String.format("%s_%s_%s", dictWord.getNatureWithFrequency(),
-                    dictWord.getWord(), dictWord.getAlias());
-            if (!wordSet.contains(key)) {
-                dimValueAlias.add(dictWord);
-            }
+        if (dimId == null || CollectionUtils.isEmpty(newWords)) {
+            return dimValueAliasMap.get(dimId);
+        }
+
+        // Use computeIfAbsent and synchronized block for thread safety
+        synchronized (dimValueAliasMap) {
+            List<DictWord> dimValueAlias =
+                    dimValueAliasMap.computeIfAbsent(dimId, k -> new ArrayList<>());
+
+            // Build deduplication key set
+            Set<String> existingKeys = dimValueAlias.stream().map(word -> buildDedupKey(word))
+                    .collect(Collectors.toSet());
+
+            // Add new words with deduplication
+            for (DictWord dictWord : newWords) {
+                String key = buildDedupKey(dictWord);
+                if (!existingKeys.contains(key)) {
+                    dimValueAlias.add(dictWord);
+                    existingKeys.add(key);
+                }
+            }
+
+            return dimValueAlias;
         }
-        dimValueAliasMap.put(dimId, dimValueAlias);
-        return dimValueAlias;
     }
 
-    public void updateSemanticKnowledge(List<DictWord> natures) {
+    /**
+     * Remove dimension value aliases by dimension ID.
+     *
+     * @param dimId dimension ID to remove, or null to clear all
+     */
+    public static void removeDimValueAlias(Long dimId) {
+        if (dimId == null) {
+            dimValueAliasMap.clear();
+            log.info("Cleared all dimension value aliases");
+        } else {
+            dimValueAliasMap.remove(dimId);
+            log.info("Removed dimension value alias for dimId: {}", dimId);
+        }
+    }
 
+    /**
+     * Build deduplication key for DictWord.
+     *
+     * @param word the DictWord object
+     * @return deduplication key string
+     */
+    private static String buildDedupKey(DictWord word) {
+        return String.format("%s_%s_%s", word.getNatureWithFrequency(), word.getWord(),
+                word.getAlias());
+    }
+
+    /**
+     * Update semantic knowledge (incremental add, no clearing). Use this method to add new words
+     * without removing existing data.
+     *
+     * @param natures the words to add
+     */
+    public void updateSemanticKnowledge(List<DictWord> natures) {
+        lock.writeLock().lock();
+        try {
+            updateSemanticKnowledgeInternal(natures);
+        } finally {
+            lock.writeLock().unlock();
+        }
+    }
+
+    private void updateSemanticKnowledgeInternal(List<DictWord> natures) {
         List<DictWord> prefixes = natures.stream().filter(
                 entry -> !entry.getNatureWithFrequency().contains(DictWordType.SUFFIX.getType()))
                 .collect(Collectors.toList());
@@ -60,52 +124,82 @@ public class KnowledgeBaseService {
         SearchService.loadSuffix(suffixes);
     }
 
+    /**
+     * Reload all knowledge (full replacement with clearing). Use this method to rebuild the entire
+     * knowledge base.
+     *
+     * @param natures all words to load
+     */
     public void reloadAllData(List<DictWord> natures) {
-        // 1. reload custom knowledge
+        // 1. reload custom knowledge (executed outside lock to avoid long blocking)
         try {
             HanlpHelper.reloadCustomDictionary();
         } catch (Exception e) {
             log.error("reloadCustomDictionary error", e);
         }
 
-        // 2. update online knowledge
-        if (CollectionUtils.isNotEmpty(dimValueAliasMap)) {
-            for (Long dimId : dimValueAliasMap.keySet()) {
-                natures.addAll(dimValueAliasMap.get(dimId));
-            }
-        }
-        updateOnlineKnowledge(natures);
-    }
-
-    private void updateOnlineKnowledge(List<DictWord> natures) {
+        // 2. acquire write lock, clear trie and rebuild (short operation)
+        lock.writeLock().lock();
         try {
-            updateSemanticKnowledge(natures);
-        } catch (Exception e) {
-            log.error("updateSemanticKnowledge error", e);
+            SearchService.clear();
+
+            if (CollectionUtils.isNotEmpty(dimValueAliasMap)) {
+                for (Long dimId : dimValueAliasMap.keySet()) {
+                    natures.addAll(dimValueAliasMap.get(dimId));
+                }
+            }
+            updateSemanticKnowledgeInternal(natures);
+        } finally {
+            lock.writeLock().unlock();
         }
     }
 
     public List<S2Term> getTerms(String text, Map<Long, List<Long>> modelIdToDataSetIds) {
-        return HanlpHelper.getTerms(text, modelIdToDataSetIds);
+        lock.readLock().lock();
+        try {
+            return HanlpHelper.getTerms(text, modelIdToDataSetIds);
+        } finally {
+            lock.readLock().unlock();
+        }
     }
 
     public List<HanlpMapResult> prefixSearch(String key, int limit,
             Map<Long, List<Long>> modelIdToDataSetIds, Set<Long> detectDataSetIds) {
-        return prefixSearchByModel(key, limit, modelIdToDataSetIds, detectDataSetIds);
+        lock.readLock().lock();
+        try {
+            return prefixSearchByModel(key, limit, modelIdToDataSetIds, detectDataSetIds);
+        } finally {
+            lock.readLock().unlock();
+        }
     }
 
     public List<HanlpMapResult> prefixSearchByModel(String key, int limit,
             Map<Long, List<Long>> modelIdToDataSetIds, Set<Long> detectDataSetIds) {
-        return SearchService.prefixSearch(key, limit, modelIdToDataSetIds, detectDataSetIds);
+        lock.readLock().lock();
+        try {
+            return SearchService.prefixSearch(key, limit, modelIdToDataSetIds, detectDataSetIds);
+        } finally {
+            lock.readLock().unlock();
+        }
     }
 
     public List<HanlpMapResult> suffixSearch(String key, int limit,
             Map<Long, List<Long>> modelIdToDataSetIds, Set<Long> detectDataSetIds) {
-        return suffixSearchByModel(key, limit, modelIdToDataSetIds, detectDataSetIds);
+        lock.readLock().lock();
+        try {
+            return suffixSearchByModel(key, limit, modelIdToDataSetIds, detectDataSetIds);
+        } finally {
+            lock.readLock().unlock();
+        }
     }
 
     public List<HanlpMapResult> suffixSearchByModel(String key, int limit,
             Map<Long, List<Long>> modelIdToDataSetIds, Set<Long> detectDataSetIds) {
-        return SearchService.suffixSearch(key, limit, modelIdToDataSetIds, detectDataSetIds);
+        lock.readLock().lock();
+        try {
+            return SearchService.suffixSearch(key, limit, modelIdToDataSetIds, detectDataSetIds);
+        } finally {
+            lock.readLock().unlock();
+        }
     }
 }
diff --git a/headless/chat/src/main/java/com/tencent/supersonic/headless/chat/knowledge/SearchService.java b/headless/chat/src/main/java/com/tencent/supersonic/headless/chat/knowledge/SearchService.java
index 8c14ffa53..247444e0c 100644
--- a/headless/chat/src/main/java/com/tencent/supersonic/headless/chat/knowledge/SearchService.java
+++ b/headless/chat/src/main/java/com/tencent/supersonic/headless/chat/knowledge/SearchService.java
@@ -31,8 +31,8 @@ import java.util.stream.Collectors;
 public class SearchService {
 
     public static final int SEARCH_SIZE = 200;
-    private static BinTrie<List<String>> trie;
-    private static BinTrie<List<String>> suffixTrie;
+    private static volatile BinTrie<List<String>> trie;
+    private static volatile BinTrie<List<String>> suffixTrie;
 
     static {
         trie = new BinTrie<>();
diff --git a/headless/chat/src/main/java/com/tencent/supersonic/headless/chat/knowledge/helper/HanlpHelper.java b/headless/chat/src/main/java/com/tencent/supersonic/headless/chat/knowledge/helper/HanlpHelper.java
index 4e6730a6b..05502f4ea 100644
--- a/headless/chat/src/main/java/com/tencent/supersonic/headless/chat/knowledge/helper/HanlpHelper.java
+++ b/headless/chat/src/main/java/com/tencent/supersonic/headless/chat/knowledge/helper/HanlpHelper.java
@@ -100,8 +100,6 @@ public class HanlpHelper {
             FileHelper.deleteCacheFile(HanLP.Config.CustomDictionaryPath);
             FileHelper.resetCustomPath(getDynamicCustomDictionary());
         }
-        // 3.clear trie
-        SearchService.clear();
 
         boolean reload = getDynamicCustomDictionary().reload();
         if (reload) {