China southwest area locates at the edge of Qinghai-Tibet plateau and is close to east side of collision zone between India plate and Eurasian plate where the geologic structure is quite complicated with serious geologic hazard. Combined with the survey and design, construction and operation of such important trunk railway lines as Bao-Cheng railway, Gui-Kun railway, Cheng-Kun railway, Xiang-Yu railway, Nan-Kun railway, Nei-Kun railway and Yu-Huai railway, etc., in complicated southwest mountainous region, the general condition of geologic hazard of southwest railway is summarized and the railway geologic survey and engineering control technique experience for several kinds of main geologic hazard are systematically presented.