The invention discloses a system for checking a voltage transformer in a GIS (gas insulated switchgear). The system comprises an intelligent frequency conversion control power supply, an excitation transformer, a high voltage automatic compensation reactor, an integrated high voltage standard voltage transformer, an intelligent field calibrator and a load box. An output end of the intelligent frequency conversion control power supply is connected with an input terminal of the excitation transformer. An output terminal of the excitation transformer is connected with a low voltage terminal of the high voltage automatic compensation reactor. A high voltage terminal of the high voltage automatic compensation reactor is connected with a high voltage end of the voltage transformer in the GIS. A high voltage terminal of the voltage transformer in the GIS is connected in parallel with the external integrated high voltage transformer. The intelligent frequency conversion control power supply further has a motor driving mechanism which is connected with the high voltage automatic compensation reactor through a signal control line. The system for checking the voltage transformer in the GIS has very high compensation efficiency, good power supply waveforms, does not have recovery overvoltage, and prevents secondary breakdown of the equipment.