Abstract: As urbanization gets into faster development, geoelectric field observation is affected by the electric signals from artificial interferences in Shanghai. It is difficult to distinguish such signals from signals of earthquake precursors. In this paper, the original signals of geoelectric field are decomposed by wavelet transform, and the intensity of background noise interference to original observation data are analyzed. We made a comparison between the original signals and filtered signals by analyzing Morlet wavelet transform modulus of abnormal signals, and tested the filtering effect in practical application by drawing azimuthal polarization plot. The results indicate that ① the method has a good performance in filtering background noises and the reconstructed signals of geoelectric field can well reflect the characteristics of original signals; ② the filtered signals of spontaneous electric field retain the variation tendency of original signals; ③ the reconstructed signals of geoelectric field can highlight the polarization characteristics of geoelectirc field and make the convergent polarization azimuth favorable to practical application.