Abstract: Metal oxide arrester is an important overvoltage protection device in power system,so its operating status is usually judged by live detection of its resistive leakage current. However,due to many external interference factors,it is difficult to extract the resistive leakage current completely from the full current. Its value is difficult to be measured accurately,and the measurement results usually need to be verified repeatedly. Therefore,a simulation model of the 220 kV metal oxide arrester is constructed in this paper,by simulating the resistive leakage current extracted when the grid voltage is zero. The harmonic method is used for analysis,and the results prove that this method can effectively reduce the disturbance caused by harmonic voltage and phase-to-phase coupling capacitance in the power system. Thus,the resistive leakage current is accurately extracted,which could effectively prove the accuracy of the field test results.