Abstract: The Sichuan-Tibet Railway is the most challenging railway project ever in the world. The project region is characterized by various adverse geological conditions including active tectonic movement, intensive mega faults, abrupt topographic relief and frequent geological disasters. Therefore, the construction of this project is challenged by complex geological disaster risks from both ground surface and underground. This study comprehensively and quantitatively analyzes the ground surface and underground geological risks along the Sichuan-Tibet Railway, and further evaluates their consequential influences on the project so as to support its feasibility study. The risk analysis utilizes abundant spatial-temporal data, and various approaches including three-dimensional structure modeling, numerical modeling, statistical modeling, dynamic modeling, time series modeling and spatial distribution modeling. The results show that there are three areas concentrated with high ground surface geological hazards risk along the Sichuan-Tibet railway, namely the Xianshuihe fault zone, the Jinshajiang fault zone and the eastern Himalayan syntaxis area. However, ground surface engineering risks of this project are significantly reduced, because its underground tunnels are over 80% of the total railway line length. The universal quantitative risk assessment models are developed for major underground engineering geological risks, including fault activities, rock bursts and large deformations. For several major tunnels such as the Yigong tunnel, risks of typical individual underground geological hazards(e.g. rock burst and large deformation) as well as the integrated risk, are quantitatively evaluated. The results show that both surface and subsurface engineering risks are significant and can threaten the safety of project. This study provides a scientific and technical support for the feasibility study of the Sichuan-Tibet Railway, and is also expected to be a reference for major engineering geological risk control for similar line engineering projects around the world.