Abstract: The accurate observation of earth resistivity is an effective method for earthquake prediction. In the face of increasingly severe electromagnetic interference, a method of ground resistivity observation based on coded source circular cross-correlation identification is proposed. The measured geoelectrical structure can be treated as the system to be identified, using the coded current signal excited by power supply electrodes A and B as the input signal of the system, and the voltage signal between the electrodes M and N is the system output response, and the input and output signals are synchronously sampled into the time series, then a reference signal is generated according to sampled coded current time series. Next, the circular cross-correlation operation between input signal and the reference signal, and between output signal and the reference signal were performed separately, and the cross-correlation time series were converted into the frequency domain by fast Fourier transform and the apparent resistivity spectrum (amplitude and phase) of the earth to be detected can be deduced. A short experiment using this method was carried out at two stations of Lanzhou observatory and Hanwang station, the results showed that this method has a strong ability to restrain noise, and can achieve high frequency resolution and measurement accuracy. The multi-frequency apparent resistivity spectrum provides the conditions for the removal of electromagnetic coupling. The feasible technical scheme is put forward in this project, want to develop instrument, to optimize the main experimental parameters, and get a higher precision resistivity monitoring and the phase monitoring ability. The result can provide the data support for the study of the characteristics of time, location and intensity of seismic anomaly information and its relationship with strong earthquakes, and it also has practical significance and application value in the field of earthquake prevention and disaster reduction.