The invention discloses a GIS/GIL voltage withstanding and partial discharge test method and device under multi-voltage superposition. The device comprises a test article, an impulse voltage branch, aDC voltage branch, an AC voltage branch, a resistor-capacitor voltage divider, and a partial discharge detection device, wherein the test article is parallelly connected with the impulse voltage branch, the DC voltage branch, the AC voltage branch and the resistor-capacitor voltage divider; one end of the test article is grounded; the impulse voltage branch comprises an impulse voltage generator,a protection ball gap and an isolation capacitor; the impulse voltage generator, the protection ball gap and the isolation capacitor are serially connected; the AC voltage branch comprises an AC voltage generator and an AC protection resistor which are serially connected; the DC voltage branch comprises a DC voltage generator and a DC protection resistor which are serially connected; and the partial discharge detection device is used for detecting the discharge characteristics of the test article. Compared with the prior art, the method and the device disclosed in the invention can detect GIS/GIL insulation defects more comprehensively, and the detection process is simple and convenient.