Because the traditional workspace analysis method is limited to the theoretical computation, and the workspace analysis is the foundation of the mechanism design and the movement control, therefore the SimMechanics was used to established the 4RRR redundant parallel mechanism three dimensional simulation kinematics model, which workspace was carried on the simulation research. Then the workspace of the mechanism was obtained by using the numerical example to drive the influence factor of the rod and the follower. The results show that the workspace of the mechanism is symmetrical and there is no empty inside; when λ gradually increasing, the workspace of the mechanism increases gradually, when λ>06,the hole at the boundary is increased, the singular position of the mechanism is increased. Compared with the workspace of the 3RRR parallel mechanism, the reachable workspace of the mechanism is obviously increased, which indicates that the introduction of redundancy is an effective method to solve the singularity of the 3RRR parallel mechanism, and increase the workspace of the parallel mechanism.