In the study of gas hydrate-related Slipstream submarine slide, the finite element analysis software ANSYS is used to construct the 3D model with complicated submarine slump topography acquired by multibeam sounding system. The lower part of sliding surface buried by slump accumulation is estimated from the main scarp geometry, and the original ground surface before slump is reconstructed according to the morphological similarity of surrounding ridges. Then, the high precision 3D geological model is automatically completed by running Jscript file in ANSYS Workbench, which greatly improves the efficiency of complex geometric modeling and thus provides a key guarantee for the accuracy of subsequent finite element numerical analysis. The stability simulation of Slipstream Ridge under its self-weight condition showes that the maximum shear stress in sediments above a shallow gas hydrate concentration layer at about 100 meters below seafloor is distributed as a series of high value bands in wedge shape, which matches well with the stepped topography observed on the current slump surface and verifies the accuracy of the 3D geological model and the validity of the proposed modeling method.