Abstract: In order to reduce the sudden change,improve the motion stability of the manipulator and increase its operational accuracy in fault tolerance,this paper defines the sudden change in joint velocity as an index and a corresponding fault tolerant planning algorithm based on this index is proposed.Then an experiment platform is built up with a PowerCube manipulator and an Optotrak motion measurement system.And the trajectory error of the manipulator's end-effector caused by the sudden change is detected with this platform. Simulation results show that the sudden change in joint velocity does occur when a redundant manipulator per- form a fault olerant operation for locked joint failures.The algorithm proposed here can effectively minimize the sudden change.