Based on the 500kV Chongwen-Zijing transmission line project, this paper discusses the technical approaches of 3D panoramic visualization of Extrahigh-Voltage (EHV) transmission line project. These approaches include the following: Firstly, the geomorphologic model of transmission line project is generated by using satellite image data and high-precision digital elevation data (DEM). Secondly, the slope photography technology is used to model the real scene of important buildings and ground objects in sensitive areas. Thirdly, BIM Technology is used to model transmission tower and transmission line. Finally, the SuperMap 3D Designer engine is used to fuse the geomorphologic model, the slop photography model and BIM model. In this way, three-dimensional panoramic display from different angles can be realized, such as provincial and municipal perspective, village and town perspective, tower perspective, etc. The research results show that the three-dimensional modeling technology based on the integration of GIS, slope photography, BIM model and three-dimensional engine technology can comprehensively display the landform of EHV transmission line project, truly reflect the crossing situation, and provide support for the fine management of EHV transmission line project.