The invention relates to an AC withstand voltage testing device, specifically a able GIS terminal integral prefabricated AC withstand voltage testing device, which belongs to the technical field of AC withstand voltage tests. The cable GIS terminal integral prefabricated AC withstand voltage testing device comprises a flange, an insulating barrel body, an insulating cover body and a wire outlet rod, wherein the inner side of the front end of the flange is fixedly connected with the insulating barrel body through a glue, the front end of the insulating barrel body is connected with the insulating cover body, the center of the insulating cover body is provided with the wire outlet rod, a threaded hole is formed in the rear end surface of the flange, a bolt can be connected in the threaded hole, and the flange is integrally connected with a GIS terminal through the bolt. The cable GIS terminal integral prefabricated AC withstand voltage testing device is simple, compact and reasonable structure, satisfies the requirements on electrical and mechanical performances, and has the advantages of reliable performance and reasonable design margin; and the insulating barrel body, the insulating cover body and the wire outlet rod are integrally formed through a casting process, thereby reducing installation steps between components, reducing shaft seal between the components, saving installation time, and improving sealing reliability of the device.