diff --git a/README.md b/README.md
index a450f76..5cbda02 100644
--- a/README.md
+++ b/README.md
@@ -16,11 +16,17 @@ This operator uses Facebook's [Detectron2](https://github.com/facebookresearch/d
 import towhee
 
 towhee.glob('./towhee.jpg') \
-      .image_decode.cv2() \
+      .image_decode() \
       .object_detection.detectron2(model_name='retinanet_resnet50') \
       .show()
 ```
 
+| Image | `boxes` | `classes` | `scores` |
+| ----- | ------- | --------- | -------- |
+| ![](example.jpg) | array([2645.9973 , 1200.3245 , 3176.163  , 2722.6785 ]) | array([0]) | array([0.9998573]) |
+
+
+
 ## Factory Constructor
 
 Create the operator via the following factory method
@@ -29,10 +35,33 @@ Create the operator via the following factory method
 
 **Parameters:**
 
-***model_name:*** *str*
+***model_name:*** `str`
 
-A string indicating which model to use.
+A string indicating which model to use. Available options:
 
-***thresh:*** *float*
+1. `faster_rcnn_resnet50_c4`
+2. `faster_rcnn_resnet50_dc5`
+3. `faster_rcnn_resnet50_fpn`
+4. `faster_rcnn_resnet101_c4`
+5. `faster_rcnn_resnet101_dc5`
+6. `faster_rcnn_resnet101_fpn`
+7. `faster_rcnn_resnext101`
+8. `retinanet_resnet50`
+9. `retinanet_resnet101`
+
+***thresh:*** `float`
 
 The threshold value for which an object is detected (default value: `0.5`). Set this value lower to detect more objects at the expense of accuracy, or higher to reduce the total number of detections but increase the quality of detected objects.
+
+### Interface
+
+This operator takes an image as input. It first detects the objects appeared in the image, and generates a bounding box around each object.
+
+**Parameters:**
+
+​  **img**: `towhee._types.Image`
+    Image data wrapped in a (as a Towhee `Image`).
+
+**Return**: `List[numpy.ndarray[4], ...], List[str], numpy.ndarray`
+
+The return value is a tuple of `(boxes, classes, scores)`. `boxes` is a list of bounding boxes. Each bounding box is represented as a 1-dimensional numpy array consisting of the top-left and the bottom-right corners, i.e. `numpy.ndarray([x1, y1, x2, y2])`. `classes` is a list of prediction labels for each bounding box. `*scores*` is a list of confidence scores corresponding to each class and bounding box.
diff --git a/detectron2.py b/detectron2.py
index a3f64a3..52e4c93 100644
--- a/detectron2.py
+++ b/detectron2.py
@@ -23,8 +23,8 @@ CFG_YAMLS = {
 }
 
 
-@register(outputschema=['boxes', 'classes', 'scores'],
-          flag=OperatorFlag.STATELESS | OperatorFlag.REUSABLE)
+@register(output_schema=['boxes', 'classes', 'scores'],
+          flag=OperatorFlag.STATELESS | OperatorFlag.REUSEABLE)
 class Detectron2(NNOperator):
     """
     This Operator implements object detection using the Detectron2 library.
@@ -34,11 +34,12 @@ class Detectron2(NNOperator):
             Detectron2-based model to use. For a full list, see `CFG_YAMLS`.
     """
 
-    def __init__(self, model_name: str = 'retinanet_resnet50', thresh: int = 0.5):
+    def __init__(self, model_name: str = 'faster_rcnn_resnet50_c4', thresh: int = 0.5):
         super().__init__()
 
         cfg = get_cfg()
         cfg.merge_from_file(model_zoo.get_config_file(CFG_YAMLS[model_name]))
+        cfg.MODEL.WEIGHTS = model_zoo.get_checkpoint_url(CFG_YAMLS[model_name])
         cfg.MODEL.DEVICE = 'cuda:0' if torch.cuda.is_available() else 'cpu'
         cfg.MODEL.RETINANET.SCORE_THRESH_TEST = thresh
         cfg.MODEL.ROI_HEADS.SCORE_THRESH_TEST = 0.5
@@ -51,6 +52,7 @@ class Detectron2(NNOperator):
 
         # Detectron2 uses BGR-formatted images
         res = self._predictor(image.to_ndarray()[:,:,::-1])
+        res = res['instances']
         boxes = res.get('pred_boxes').tensor.numpy()
         classes = res.get('pred_classes').numpy()
         scores = res.get('scores').numpy()
diff --git a/example.jpg b/example.jpg
new file mode 100644
index 0000000..f36248d
Binary files /dev/null and b/example.jpg differ