With the development of multi-beam sounding technique and point clouds processing technology, more and more elaborate simulation of underwater terrain tended to be possible. Combined with underwater riprap revetment engineering, this paper first briefly introduced the working principle and data processing flow of multi-beam sounding system, and then analyzed some key processing techniques of simulating underwater terrain, such as point cloud acquisition, point cloud filtering, point cloud compression and 3D model construction, lastly showed the simulation effect by the instance. The experimental results showed that the methods of curvature compression and Delaunay triangulation network had good applicability in building 3D models of underwater topography. From the perspective of the constructed 3D model, the underwater topography simulation could not only directly express the actual form of the underwater topography, but also played a good role in assisting the quality inspection and operation management of related water conservancy projects.