Due to the limited detection range of optical sensors in the ocean, sonar stands out as the predominant method for detecting dynamic objects in the deep sea. Since there is stronger reflection underwater, the objects are more salient in sonar images compared to the background. In this paper, we propose a saliency detection framework for underwater moving object, which consists of three stages. In the first stage, we use optical flow to get rough global motion cues under background interference in unstable sonar platforms.