The force transmission performance of manipulator is studied, the concept of force transmission capacity is proposed. A multi-object optimize function consisted of workspace > kinematics performance and force transmission performance is established and applied in optimize design of a three DOF haptic device; The workspace, kinematics performance force transmission of manipulator optimized are analyzed, parameters of structure and drive are decided, the prototype is manufactured eventually. The analysis and method of optimizing would provide references for developing of other haptic devices with outstanding performance.