This article in view of the different scale changes lead to the detect ion rate of weld defect effect is not ideal,is proposed based on a faster region-based convolutional neural network (Faster R-CNN) of weld defect detection algorithm of improved algorithm using convolution expansion characteristics under the diff erent expansion rate,combination of convolution kernels under different receptive field more co mprehensive to extract the feature information of different scales,to improve the target detec tion accuracy at the same time,the deep separable convolution is used to compress the model to impro ve the detection speed.The experiment shows that the improved network can improve the detection speed while ensuring the operation speed and the detection accuracy can reach 72%.