A GIS electronic transformer test system based on disconnecting switch switching-on and switching-off capacitive small current comprises a high-voltage test transformer and a capacitive voltage divider connected on a BSG sleeve, a load capacitor on the other BSG sleeve, a disconnecting switch between the two sleeves, calibrating primary transient state test system and an electronic transformer to be tested, one end of a secondary converter is connected with the electronic transformer to be tested, the other end is connected with a merging unit, and the other end of the merging unit is connected with a fault recorder. Voltage values and current valves on a high voltage bus are tested when the disconnecting switch is switched on and switched off, thereby being compared with output of the electronic transformer to be tested. Through the test system, electromagnetic environments of 110KV, 220KV, and 500KV voltage classes in power transmission and power cut-off processes can be simulated, the process of the field disconnecting switch switching on and switching off an empty lead and a capacitive small current load is simulated, analogous field transient state strong interference is generated, and the electromagnetic protective performance of the electronic transformer is examined under such conditions.