Abstract: In geophysical exploration work on bad geologic body of deep-long tunnel, controlled source audio frequency magnetotellurics method (CSAMT) is fairly effective one of detecting such bad geologic bodies. However, CSAMT data is affected badly by static effect in complex terrain, and whether the effect of static correction is good or not is crucial for interpretation results. Based on reviewing the relative references on static correction this paper presents a correction method of EMAP method combined with all profile comparison method. Then a case study has been carried out in one revised railway tunnel of southwestern China, and the result is well verified by boreholes and relative geologic information, which indicates that this corection method is effective in CSAMT data processing, and CSAMT method is feasible for analysis of rock property of tunnel line. Therefore CSAMT method is an instructive guide for tunnel digging.