Industrial robots have been increasingly applied to aircraft automation assembly lines due to their high flexibility and low cost, but poor absolute positioning accuracy of industrial robot is the bottleneck that constrains their development. In order to further improve the positioning accuracy of the robot, a positioning accuracy method based on mechanical joint feedback is proposed. This method is applied to control the robot by installing the absolute gratings at the joints and the semi-closed-loop control is established for reducing the effect of the joint error on the position of the end effector and increasing the positioning accuracy of joints. The experimental result shows that the absolute error of the robot is reduced from 1.125mm to 0.167mm. This method can effectively improve the absolute positioning accuracy of the robot and realizes the high precision control of the robot.