The invention discloses a blade diffuser adjustment mechanism of a centrifugal compressor and a control method thereof, which are suitable for the testing field of a centrifugal compressor of a compressed air energy storage system, and include a cap, a rotating handle, a set screw, a jacket, a distance sleeve, a deep Groove ball bearings, bushings, diffuser blades, etc., can manually adjust the installation angle of the diffuser blades. The main advantage of the present invention is that the adjustment mechanism of the vane diffuser is manually adjusted, without complex actuators and transmission linkages, etc., while reducing the complexity of the device, it can avoid interference to the flow field inside the volute; the vane diffuser The compressor adjustment mechanism is equipped with dials, metal pointers, etc., which can avoid control errors caused by the actuator and improve the accuracy of the compressor test results.