Abstract: The Stewart parallel platform with 6 degree of freedoms (6-DOFS), which has the advantages of big bearing capacity,high control accuracy and strong structure stiffness, has been widely used in military equipment, astronautics and industry applications.Meanwhile, its inherent defects, such as small workspace, poor dexterity and the singularity configurations, have constrained its further application. In this paper structure optimization and force analysis were carried out based on kinematics and dynamic simulation results using enumeration method, to improve the positioning accuracy, structure stiffness and expend the workspace under constrained boundary condition. Finally, the inherent defects could be resolved and the comprehensive performance could be improved, and thus the system could be further used in automatic docking applications.