Aiming at the problems of low accuracy and large shape error of existing models for single-course resistance torque of spacesuit soft joints, an improved Bouc-Wen mathematical model was established. By analyzing the hysteresis curves characteristics of single-course resistance torque of spacesuit soft joints, the Bouc-Wen hysteresis model was introduced and improved to eliminate the redundancy and symmetry of the model, which was used to characterize single-course resistance torque of soft joints mathematically. The individual genetic process of multi-island genetic algorithm was operated by using the probability thought of simulated annealing algorithm to identify the parameters of improved Bouc-Wen model with high accuracy and efficiency. Based on the verification of experiments and simulations of different soft joints of spacesuit, the improved Bouc-Wen model compared with the Jiles-Atherton model is more suitable for the mathematical characterization of single-course resistance torque of spacesuit soft joints. The variance of resistance torque of improved Bouc-Wen model is two orders of magnitude lower than that of Jiles-Atherton model. It shows that the mathematical model has high accuracy when applied to single-course resistance torque of spacesuit soft joints, and has strong applicability to different soft joints of spacesuit.