diff --git a/metal/paddle-mobile/paddle-mobile/Operators/BoxcoderOp.swift b/metal/paddle-mobile/paddle-mobile/Operators/BoxcoderOp.swift
index 4cea0c7c58b8ff89196d49962eca2624d1fed6a1..f50664dd1a7c165c5df06965cdca992492a86650 100644
--- a/metal/paddle-mobile/paddle-mobile/Operators/BoxcoderOp.swift
+++ b/metal/paddle-mobile/paddle-mobile/Operators/BoxcoderOp.swift
@@ -27,6 +27,11 @@ class BoxcoderParam<P: PrecisionType>: OpParam {
         } catch let error {
             throw error
         }
+        assert(priorBox.transpose == [0, 1, 2, 3])
+        assert(priorBoxVar.transpose == [0, 1, 2, 3])
+        assert(targetBox.transpose == [0, 1, 2, 3])
+        assert(codeType == "decode_center_size") // encode_center_size is not implemented
+        assert((targetBox.tensorDim.cout() == 3) && (targetBox.tensorDim[0] == 1)) // N must be 1 (only handle batch size = 1)
     }
     let priorBox: Texture<P>
     let priorBoxVar: Texture<P>
diff --git a/metal/paddle-mobile/paddle-mobile/Operators/Kernels/BoxcoderKernel.swift b/metal/paddle-mobile/paddle-mobile/Operators/Kernels/BoxcoderKernel.swift
index 461652e8c3e53114b36b89a4be785443d3756dcc..26d9c2cdf64ced43ec459b4a2de8304ff37dc222 100644
--- a/metal/paddle-mobile/paddle-mobile/Operators/Kernels/BoxcoderKernel.swift
+++ b/metal/paddle-mobile/paddle-mobile/Operators/Kernels/BoxcoderKernel.swift
@@ -14,18 +14,26 @@
 
 import Foundation
 
+struct BoxcoderMetalParam {
+}
+
 class BoxcoderKernel<P: PrecisionType>: Kernel, Computable{
     func compute(commandBuffer: MTLCommandBuffer, param: BoxcoderParam<P>) throws {
         guard let encoder = commandBuffer.makeComputeCommandEncoder() else {
             throw PaddleMobileError.predictError(message: " encode is nil")
         }
-//        encoder.setTexture(param.input.metalTexture, index: 0)
-        encoder.setTexture(param.output.metalTexture, index: 1)
+        encoder.setTexture(param.priorBox.metalTexture, index: 0)
+        encoder.setTexture(param.priorBoxVar.metalTexture, index: 1)
+        encoder.setTexture(param.targetBox.metalTexture, index: 2)
+        encoder.setTexture(param.output.metalTexture, index: 3)
+        var bmp = BoxcoderMetalParam.init()
+        encoder.setBytes(&bmp, length: MemoryLayout<BoxcoderMetalParam>.size, index: 0)
         encoder.dispatch(computePipline: pipline, outTexture: param.output.metalTexture)
         encoder.endEncoding()
     }
     
     required init(device: MTLDevice, param: BoxcoderParam<P>) {
+        param.output.initTexture(device: device)
         super.init(device: device, inFunctionName: "priorbox")
     }
 }
diff --git a/metal/paddle-mobile/paddle-mobile/Operators/Kernels/Kernels.metal b/metal/paddle-mobile/paddle-mobile/Operators/Kernels/Kernels.metal
index 234fbd0fd61fed4def08a3526a4b5fe17aae80fc..a00c7a71a466b6754d0aa52f94bf99bb03531373 100644
--- a/metal/paddle-mobile/paddle-mobile/Operators/Kernels/Kernels.metal
+++ b/metal/paddle-mobile/paddle-mobile/Operators/Kernels/Kernels.metal
@@ -477,3 +477,18 @@ kernel void concat(texture2d_array<float, access::read> in0 [[texture(0)]],
     }
     out.write(r, gid.xy, gid.z);
 }
+
+kernel void boxcoder(texture2d_array<float, access::read> priorBox [[texture(0)]],
+                     texture2d_array<float, access::read> priorBoxVar [[texture(1)]],
+                     texture2d_array<float, access::read> targetBox [[texture(2)]],
+                     texture2d_array<float, access::write> output[[texture(3)]],
+                     uint3 gid [[thread_position_in_grid]]) {
+    float4 t = targetBox.read(gid.xy, gid.z);
+    float4 p = priorBox.read(gid.xy, gid.z);
+    float4 pv = priorBoxVar.read(gid.xy, gid.z);
+    float ox = (p.z * pv.x * t.x + p.x) - t.z / 2;
+    float oy = (p.w * pv.y * t.y + p.y) - t.w / 2;
+    float ow = exp(pv.z * t.z) * p.z + t.z / 2;
+    float oh = exp(pv.w * t.w) * p.w + t.w / 2;
+    output.write(float4(ox, oy, ow, oh), gid.xy, gid.z);
+}