Abstract: The Baode HVDC transmission project passes through three provinces of Shaanxi, Gansu and Sichuan, and the additional electric field signals generated can be recorded by multiple geoelectric field observation stations located in six provinces（cities and districts）including Shaanxi, Gansu, Ningxia, Sichuan, Shanxi and Chongqing. In this paper, the variation characteristics of geoelectric field observation data in different areas on both sides and both ends of the line are studied, and it is found that the additional electric field shows certain characteristics in the variation direction, amplitude, morphology and spatial distribution. Aiming at the above change characteristics, this paper discusses the influence mechanism of HVDC transmission on the observation of geoelectric field and the geological conditions of geoelectric field station, in order to deepen the understanding of the change characteristics of seismic electric signal.