Aiming to identify the inertial parameter of parallel robots, an improving method for the kinematics analysis of 6—SPR was proposed. First, by using the methods similar to series robot, the special position of each component in each branch was determined for constructing influence coefficient matrixes. Second, the barycentric coordinates were separated from the matrixes with proper simplifications. Then the motions of components can be linked linearly with its barycentric coordinates. An example about upper mounting plate’s motion was simulated by the ADAMS software to show the effectiveness of the method. 