Aiming at the problem of high missing rate and weak generalization ability of small targets detection in SAR image by traditional detection methods, this paper proposes a small target algorithm of sea surface based on improved YOLO-v5 SAR image. First production of a wide range of ports and sea small target data set, and then the characteristics of the data set to improve optimization of deep learning network, including through adaptive algorithm convergence speed and improve model anchor box detection effect, increase the residual network to stem the spread of deep neural network gradient disappeared and excessive fitting, add different neural network model. The experimental results show that the miss detection rate of yolov5 is 1.78% lower than that of yolov3, and it has a lighter model than yolov4 model.