Abstract: The detection range of the hanging sonar is not only related to the performance of the equipment and the characteristics of the marine acoustic environment, but also affected by the seabed topography. In this paper, the acoustic propagation characteristics of two typical seabed topographies (undersea mountain and basin) of different heights and depths are simulated and analyzed by ray acoustic model under the sound velocity profile of positive gradient and the sound velocity profile with a leaping layer. Based on the characteristics of acoustic propagation, the influences of the two typical seabed topographies on the detection distance of hanging sonar are obtained. According to the characteristics of acoustic propagation, the approximate navigational areas of submarine avoiding sonar search under different undersea terrain are obtained, and the feasible scheme to increase the submarine search probability of hanging sonar is given.