Abstract: Aiming at the requirements of verifying the deployment performance of the space deployable arm joints under thermal vacuum, a vacuum-thermal-mechanical coupling test method for deployable arm joint was proposed. The thermal vacuum test system was used to simulate the vacuum, cold black and solar radiation environment. The load was applied by an external quantitative inertia disk. The test result show that the vacuum degree, the temperature and the temperature control accuracy of the tank body all meet the test requirements. Under high and low temperatures, the working current of the deployable arm joint fluctuates randomly, and the fluctuation range is within the safe margin of the design current. Before and after the test, there is no significant change in the starting torque of the deployable arm joint, the maximum joint revolving speed and the pointing accuracy, in which the accuracy is better than 0.001°. This method may provide technical support for the subsequent vacuum-thermal-mechanical coupling test of the deployable arm joint.