The present invention provides a cover plate test device for the connection air chamber of an oil-gas type transformer and a GIS. The device comprises an insulating plate fixedly connected with a connection air chamber, and a bellows fixed on the insulating plate inside the connection air chamber. The insulating plate is provided with a positioning pin for fixing a dynamic test conductive rod. The bellows is fixedly connected with the dynamic test conductive rod. The dynamic test conductive rod passes through the insulating plate and the bellows to be connected with a concave type contact. The insulating plate is provided with a grounding terminal. The grounding terminal is arranged in a sealing cover. Since the cover plate test device for the connection air chamber can be realized on the basis of an original cover plate aperture, the purposes of easy modification, simple operation, safety and reliability are realized. The working efficiency and the reliability of power supply are effectively improved. Meanwhile, the personal safety is ensured maximally.