diff --git a/backend/app/rag/pipeline.py b/backend/app/rag/pipeline.py
index 2d89801..b6f8727 100644
--- a/backend/app/rag/pipeline.py
+++ b/backend/app/rag/pipeline.py
@@ -70,6 +70,13 @@ class RAGPipeline:
             content_len = len(doc.page_content)
             info(f"[Pipeline]   子文档[{i}] 长度={content_len}字符")
 
+        # Step 1.5: 向量初筛（进入重排前先过滤）
+        vector_top_n = 20
+        info(f"[Pipeline] Step 1.5: 向量初筛: 取前 {vector_top_n} 个（当前 {len(child_docs)} 个）")
+        if len(child_docs) > vector_top_n:
+            child_docs = child_docs[:vector_top_n]
+            info(f"[Pipeline] Step 1.5 完成: 向量初筛后 {len(child_docs)} 个")
+
         # Step 2: 重排
         info(f"[Pipeline] Step 2: 开始重排")
         if self.reranker: