The center pointer and pose of work-piece are given by image processing and are transformed to the robot coordinate by a simple and high precise mapping algorithm. The depth of work-piece is obtained by ultrasonic range measurement. The data fusion of center pointer, pose and depth of the work-piece and the control input-vector of robot is computed out. The robot movement is precisely controlled by the control input-vector and work-piece is precisely grasped. The low error of image processing and high precision of depth measurement ensure that the grasping is highly precise.