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 B-W(Bouc-Wen) mathematical model was established. By analyzing the hysteresis curve characteristics of single-course resistance torque of spacesuit soft joints, the B-W 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 B-W model with high accuracy and efficiency. Based on the verification of experiments and simulations of different soft joints of spacesuit, the improved B-W model compared with the J-A(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 B-W model is two orders of magnitude lower than that of J-A 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.