3PSS parallel mechanism is one of the most utility outlook mechanisms among the parallel mechanism, but analysis and development to it is too inadequate. In this paper, analysis of the structure and degrees of freedom to it have been done, the inverse solution to the position analysis of the mechanism was solved by closed method and the forward solution to the position analysis was solved by numerical method. The singularity and the velocity of the mechanism were analyzed by Jacobian matrix, and the simulation of it was done, this established a good foundation for the determination of the work rule and the path-planning of 3PSS parallel mechanism