According to the requirement of a given parallel mechanism end actuator and to make sure that kinematics transmission performance of each branch is relatively better in optimum design of its structure parameters，local and global motion (speed), force and power distribution performance indicators were defined by using the character of dispersion, which reflected the ability of branch to share the load requirements. For a single drive branch power output, the effect of speed and force was discussed which were both variable physical quantities on power, and the movement and force coefficient were defined. The workspace of parallel mechanism was analyzed by using those parameters. Finally the 3-RPS parallel mechanism for attitude adjustment components was used as an example. And a detailed solution to the above indicators was developed. Performance atlas in the modified design space was overlaid，the structural parameters of the mechanism were optimized and the corresponding workspace was found out. The motion, force and power distribution performance indicators can be further applied to the performance analysis of other parallel mechanisms, as well as to guide optimization design of parameters. Each branch of the parallel mechanism obtained through this optimization method has good power, motion and force transmission performance. This sets the foundation for the kinematics and dynamics analysis of parallel mechanism.