diff --git a/easy-agents-store/easy-agents-store-milvus/src/main/java/com/easyagents/store/milvus/MilvusPrimaryKeySupport.java b/easy-agents-store/easy-agents-store-milvus/src/main/java/com/easyagents/store/milvus/MilvusPrimaryKeySupport.java
new file mode 100644
index 0000000..6d1ff1c
--- /dev/null
+++ b/easy-agents-store/easy-agents-store-milvus/src/main/java/com/easyagents/store/milvus/MilvusPrimaryKeySupport.java
@@ -0,0 +1,39 @@
+package com.easyagents.store.milvus;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.Objects;
+
+/**
+ * Milvus VarChar 主键转换工具。
+ */
+final class MilvusPrimaryKeySupport {
+
+    /**
+     * 禁止实例化无状态工具类。
+     */
+    private MilvusPrimaryKeySupport() {
+    }
+
+    /**
+     * 将删除主键归一化为 Milvus VarChar 主键值。
+     *
+     * <p>Milvus 向量存储创建的集合固定使用 VarChar 类型的 {@code id} 主键。
+     * Java SDK 会根据传入值类型生成删除表达式，因此数值对象必须先转为字符串。</p>
+     *
+     * @param ids 调用方提供的主键集合
+     * @return 可直接传给 Milvus Java SDK 的字符串主键列表
+     * @throws NullPointerException 主键集合中包含空值时抛出
+     */
+    static List<Object> normalize(Collection<?> ids) {
+        List<Object> normalizedIds = new ArrayList<Object>(ids.size());
+        for (Object id : ids) {
+            normalizedIds.add(Objects.requireNonNull(
+                id,
+                "Milvus primary key must not be null"
+            ).toString());
+        }
+        return normalizedIds;
+    }
+}
diff --git a/easy-agents-store/easy-agents-store-milvus/src/main/java/com/easyagents/store/milvus/MilvusVectorStore.java b/easy-agents-store/easy-agents-store-milvus/src/main/java/com/easyagents/store/milvus/MilvusVectorStore.java
index aed63f1..efee8fc 100644
--- a/easy-agents-store/easy-agents-store-milvus/src/main/java/com/easyagents/store/milvus/MilvusVectorStore.java
+++ b/easy-agents-store/easy-agents-store-milvus/src/main/java/com/easyagents/store/milvus/MilvusVectorStore.java
@@ -157,12 +157,14 @@ public class MilvusVectorStore extends DocumentStore implements AutoCloseable {
             }
             DeleteReq deleteReq = builder
                 .collectionName(collectionName)
-                .ids(new ArrayList<Object>(ids))
+                .ids(MilvusPrimaryKeySupport.normalize(ids))
                 .build();
             client.delete(deleteReq);
             return StoreResult.success();
         } catch (Exception e) {
-            return StoreResult.fail();
+            LOG.error("Milvus delete failed. collection={}, message={}",
+                collectionName, e.getMessage(), e);
+            return StoreResult.fail(e.getMessage());
         }
     }
 
diff --git a/easy-agents-store/easy-agents-store-milvus/src/test/java/com/easyagents/store/milvus/MilvusPrimaryKeySupportTest.java b/easy-agents-store/easy-agents-store-milvus/src/test/java/com/easyagents/store/milvus/MilvusPrimaryKeySupportTest.java
new file mode 100644
index 0000000..8efa250
--- /dev/null
+++ b/easy-agents-store/easy-agents-store-milvus/src/test/java/com/easyagents/store/milvus/MilvusPrimaryKeySupportTest.java
@@ -0,0 +1,42 @@
+package com.easyagents.store.milvus;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.math.BigInteger;
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * {@link MilvusPrimaryKeySupport} 主键归一化测试。
+ */
+public class MilvusPrimaryKeySupportTest {
+
+    /**
+     * 验证数值和字符串主键都按 VarChar 类型传给 Milvus。
+     */
+    @Test
+    public void shouldNormalizeDeleteIdsAsStrings() {
+        List<Object> ids = MilvusPrimaryKeySupport.normalize(Arrays.asList(
+            new BigInteger("105257799143000107"),
+            42L,
+            "faq-1"
+        ));
+
+        Assert.assertEquals(
+            Arrays.asList("105257799143000107", "42", "faq-1"),
+            ids
+        );
+        for (Object id : ids) {
+            Assert.assertTrue(id instanceof String);
+        }
+    }
+
+    /**
+     * 验证空主键会被明确拒绝，避免生成无效删除表达式。
+     */
+    @Test(expected = NullPointerException.class)
+    public void shouldRejectNullDeleteId() {
+        MilvusPrimaryKeySupport.normalize(Arrays.asList("1", null));
+    }
+}