Research conclusions: In the fault structure exploration for railway，compared with the conventional geophysical methods，the natural source audio frequency magnetotellurics has the features of the rapid survey with less topographical limitation，big survey depth and low cost． With the self － developed data processing methods，the same platform can be used for processing the data of the natural source audio frequency magnetollurics and CSAMT to solve the defect that the inversion is too smooth and abnormal homogenization，getting good survey effect on the fault structure exploration and finding out the distribution pattern of fault structure． It provides a strong basis for the railway alignment and guiding significance to the similar works．