With the effect of high-voltage line on CSAMT data in a prospecting area as an example, the authors tried to find the methods of data processing on the basis of the characteristics of electromagnetic interference. This paper summarizes the characteristics of the effects of high voltage line on CSAMT data in the prospecting area. The authors recovered magnetic signal close to the normal field using interpolation method, then calculated the apparent resistivity using the original electric signal and recovered magnetic signal. Comparative studies and drilling verification demonstrate that this method is pretty good and could be used in data processing under similar conditions.