The invention discloses a 40.5kV gas-insulated switchgear transmission mechanism, which comprises a cabinet body, an input assembly, an actuator and a transmission assembly. The cabinet body is provided with a closed accommodating cavity, and a partition plate is arranged in the accommodating cavity to divide the accommodating cavity into an air box chamber and a mechanism chamber which are not communicated with each other. The input assembly is located in the mechanism chamber and comprises an input shaft and a cam, the input shaft is rotationally connected with the cabinet body, and the camsleeves the input shaft and is fixedly connected with the input shaft. The actuator is arranged in the air box chamber and is used for closing or opening the circuit. The transmission assembly comprises an outer transmission device, a pressure device, an inner transmission device and a transmission rod, wherein the pressure device is located in the mechanism chamber, one end of the transmission rod is connected with the pressure device, and the other end penetrates the partition plate to be connected with the inner transmission device. The transmission mechanism has the beneficial effect that:because the pressure device is arranged in the mechanism chamber and serves as a connecting interface of the outer transmission device and the inner transmission device, the modularization level of the transmission mechanism is improved, and the maintenance and debugging efficiency is improved.