The invention discloses a vacuum high/low temperature environmental simulation electromechanical transmission mechanism comprehensive performance experimental system, which comprises an experimental platform, a driving assembly, a vacuum high/low temperature experimental assembly, a normal temperature and normal pressure experimental assembly and a loading assembly. The driving assembly comprisesa servo motor, an input end torque and speed sensor and an input end angle encoder; the vacuum high/low temperature experimental assembly comprises vacuum high/low temperature environmental simulation equipment, an optical platform, and input and output end magnetic fluid sealing shafts; and the loading assembly comprises an output end angle encoder, an output end torque and speed sensor and a torque motor. The vacuum high/low temperature environmental simulation equipment has low cost, the installation of the driving assembly and the loading assembly is performed outside a vacuum tank, and the installation and debugging are convenient. Due to the adoption of a modular design, the experimental system can test the comprehensive performance of a speed reducer and other rotating mechanisms under the conditions of space environment and normal temperature and normal pressure environment on the same experimental system, and has the advantages of strong adaptability of the equipment and highdetection accuracy.