Asteroid exploration is of great scientific significance in understanding the evolution of the solar system. Unlike lunar missions, asteroids are far away from the earth, the communication between the spacecraft and the ground station has a large delay. Moreover, the small size, irregular shape and uneven mass distribution of asteroids further increase the difficulty of landing missions. This paper presented a topographic mapping and analysis method based on three-dimensional (3D) reconstruction model of a simulated asteroid. First, 3D reconstruction of a simulated asteroid was achieved using Structure from Motion (SfM) technique. Then Digital Elevation Model (DEM) and Digital Orthophoto Map (DOM) were produced based on the 3D point cloud data. By analysing the DEM data, we finally obtained the obstacles distribution map. In order to verify the proposed method, we used a simulated asteroid to conduct experiments. And the experimental results demonstrated the effectiveness of the developed method. The topographic mapping and analysis method presented in this study can be applied to landing/sampling area selection in further asteroid exploration research.