The mathematical model of spacesuit joint torque makes a significant disparity in the prediction of extra-vehicular activity (EVA) task intensity, fatigue estimation of astronaut and planning EVA route. Firstly, the hysteresis of joint torque is analyzed and the requirement of the joint torque model application is stated. The Jiles-Atherton hysteresis model, as well as the relevance with hysteresis property of joint torque, is detailed. Then the simulated annealing is adopted to improve the genetic algorithm, which is realized by MATLAB. Finally, the mathematical models of the EVA spacesuit wrist joint torque and shoulder joint torque are simulated. The consequence of simulation elucidates that the mathematical model of spacesuit joint torque is feasible. What is more, the mathematical model of spacesuit joint torque will have a wide application in the research of spacesuit ergonomic and other fields.