The structures of 3-PRC and 3-RPC parallel mechanism are analyzed.The movable paltform’s motion paths of the two kinds of parallel mechanism are studied by using the theory of inverse kinematics of the parallel mechanism.The computation formula of inverse kinematics are deduced according to the homogeneous transformation
then the movement rules exerted on the actuator are achieved when the movable platforms were moving on the desired trajectories.The virtual prototypes of these mechanisms are created in ProE software and the planning trajectories are verified through simulation in ADAMS at last.