In order to improve the complicated soil structure reasonable grounding location and avoid HVDC system monopole ground operation into the adverse effects of the current to the power grid, a composite soil geological model is set up for the typical fracture structure near the UHVDC grounding electrode. The calculation formula of surface potential is derived by combining the traveling wave method with the mirror image method. Based on the Matlab simulation platform, the surface potential distribution of two soil models under horizontal and composite conditions is compared, and the surface potential distribution under the influence of fracture and parameters is studied. The results show that the surface potential is closer to the measured value under the composite soil geological model. The distance from the fault to the ground electrode has great influence on the surface potential in the large area. The influence of the electrical resistivity at the fracture site is mainly considered in the near area of the grounding electrode. The conclusion is of great significance to locate the site of the ground pole and prevent the DC magnetic bias. This work is supported byNational Natural Science Foundation of China (No. 51767023) and the Natural Science Foundation of Xinjiang Uygur Autonomous Region (No. 2017D01C028).