Abstract: Based on optimal region of wheeled mobile platform and the relation between mobility and manipulability of wheeled mobile manipulator, a new optimal criterion for wheeled mobile manipulator's multi-point motion planning problem was proposed. The criterion has explicit meaning and includes not only the cost of mobile platform, the cost of manipulator, but also the cost which mobile manipulator takes to go away from it's optimal configuration and the cost which commutation configuration takes to go away from it's optimal value. Finally, the feasibility of the method was proved by simulation.