For improving the control accuracy of actuator at the end of the SCARA robot manipulator, a geometric shape coordinates new algorithm based on the motorwasher was proposed. Based on the armwasher assembly equipment of the SCARA robot designed with bionic theory, the visual processing and precision control technology research were carried out,the motor and gasket images collected by the end actuator were processed, identification and location of motor center and gasket center were completed based on template feature. According to the geometric shape of the die of the motor,a motor coordinate calculation method based on the three images was put forward. The positioning accuracy control test of the end effector was carried out and the feasibility of the algorithm was verified.The results show that the test results are far less than 02 mm required for motor assembly precision, which proves that the algorithm can be used to improve the positioning accuracy of end actuator effectively.