diff --git a/internal/nsfw/server.py b/internal/nsfw/server.py
index 57c4db2..02f7f46 100644
--- a/internal/nsfw/server.py
+++ b/internal/nsfw/server.py
@@ -189,19 +189,27 @@ def _raw_detect(det, data):
             scores.append(float(max_score))
             class_ids.append(class_id)
 
-    indices = cv2.dnn.NMSBoxes(boxes, scores, 0.1, 0.45)
+    # 没有检测到任何类别，直接返回空
+    if not boxes:
+        return []
+
+    # 转成 numpy array，OpenCV 的 NMSBoxes 需要
+    boxes_arr = np.array(boxes, dtype=np.float32)
+    scores_arr = np.array(scores, dtype=np.float32)
+
+    indices = cv2.dnn.NMSBoxes(boxes_arr.tolist(), scores_arr.tolist(), 0.1, 0.45)
 
     detections = []
-    for i in indices:
-        idx = i if isinstance(i, int) else i[0]
-        detections.append({
-            "class": __labels[class_ids[idx]],
-            "score": scores[idx],
-            "box": [int(boxes[idx][0]), int(boxes[idx][1]), int(boxes[idx][2]), int(boxes[idx][3])],
-        })
+    if indices is not None and len(indices) > 0:
+        for i in np.array(indices).flatten():
+            idx = int(i)
+            detections.append({
+                "class": __labels[class_ids[idx]],
+                "score": scores[idx],
+                "box": [int(boxes[idx][0]), int(boxes[idx][1]), int(boxes[idx][2]), int(boxes[idx][3])],
+            })
     return detections
 
-
 # NudeNet 的标签表（和 nudenet.nudenet.__labels 一致）
 __labels = [
     "FEMALE_GENITALIA_COVERED", "FACE_FEMALE", "BUTTOCKS_EXPOSED",