Research conclusions:(1)Controlled Source Audio Magneto Tellurics(CSAMT) data quality factors in addition to uncontrollable noise humanities，there is some non-human factors:the length of the error can be controlled from the electrode，the electrode spacing of the horizontal deviation of the horizontal magnetic probe bias.(2)The research of the non-humanistic noise can reduce the apparent resistivity error generated outside gathering，to obtain reliable and accurate geoelectric information.(3)The gob survey geological of railway in this researching，combined the geological problems for physical characteristics with the principles of magnetotelluric，improved the geophysical survey of the mined-out area of detection accuracy and resolution，satisfied the needs of the railway geological survey of mined-out area. (4)The research results can be used to guide the gob survey work on similar projects.