It is suitable for leak detection and SF6 gas filling of the complete machine or gas chamber of 12-40.5Kv gas insulated switchgear (C-GIS) and 7.2-12Kv ring network cabinet products. During leak detection and gas filling of the system, always keep the pressure difference between the inside and outside of the vacuum box of the workpiece and the equipment within a certain range to prevent the deformation of the workpiece. The system uses the helium mass spectrometer leak detection principle for leak detection, and judges whether the inspected workpiece is qualified or unqualified through related devices. The applied helium is recycled and reused, and finally filled with SF6 insulating gas under vacuum.