Abstract: The paper analyzed the characteristics of structural lock performing mechanism of spatial docking system and the difficulties of solving the model of the mechanism through dynamic analysis software on hand. And them the modeling method of multi-body dynamics is adopted and dynamics equation of the mechanism is established. The solving process considering the special features of the model is also narrated. Finally, the result of dynamics characteristics curves which are obtained from the model proved that the ball bearing lead screw mechanism aided by spring mechanism is feasible as the structural lock performing mechanism.