The three degreeoffreedom (3DOF) planar parallel manipulator with actuation redundancy was taken as the object of study. The theory of geometric model of the solution space was utilized to obtain the solution space of the mechanism of manipulator. Velocity Jacobian matrix and flexibility matrix of the mechanism were solved, and then the global stiffness performance evaluation indices were gotten. Base on these, the relationship between the stiffness and the kinematics lengths of the mechanism of manipulator was discussed, and the corresponding performance atlases of stiffness were plotted. The atlases are very useful for optimized design of the structure of manipulator. 