Earthquake geoelectric field observation in Beijing area is subject to serious interference from urban rail transit.In this paper,the interferences to the geo-electrical field observation data over the years from urban rail transit in Beijing area are analyzed.According to the characteristics of rail transit operation,FFT spectral analysis is performed on the seriously disturbed geoelectric field observation data of Tongzhou station to extract the data of normal variation from the geo-electric field observations;meanwhile,methods of processing of such disturbed data are also addressed.