The purpose of this research is to accomplish the optimal mechanism design of the 3-leg 6-DOF platform system. In the meantime, we derive the inverse kinematic and dynamic equations. Using these equations, we complete the real-time simulation under the RTLinux operation system. In this paper, we apply the Taguchi Experimental Method to design the optimal mechanism and use the result as the actual design data of the platform system. The platform system is constructed by three flexible staffs which are sliding on three linear motors. It appears very good performance in this configuration.