To detect the insulation defects of the GIS with special structure

acceptance test and periodic preventive test are necessary.Because of the special structure

the withstand voltage of GIS gas chamber cannot be tested by conventional methods

and the leakage current test of metal oxide arrester（MOA）is also difficult.In this study

a triple-frequency test method with electromagnetic potential transformer was proposed to test the withstand voltage of the gas charmer of 110 k V GIS

and to measure the leakage current of MOA.The influencing factors

such as capacitive voltage-augment and distributed capacitance

were analyzed during the test

and the relationship among primary current

secondary current and compensating reactance were achieved.Test results validate the proposed method.