According to the detection accuracy of the high precision photoelectric encoder corner , a photoelectrical encoder corner precision measurement method based on dual-frequency laser interferometer is proposed. This device is driven by stepping motor. Through the reduction mechanism, the inspection encoder and the angle reference can be rotated. By using the Renishaw dual-frequency laser interferometer as the angle benchmark testing instruments and Renishaw RX10 rotors calibration module as large angle rotation reference, precision of 1.36″ is obtained. Traditional manual device and the proposed device in a 21 bit absolute encoder are used respectively for precision testing. The results show that the device is feasible, and that the test efficiency and precision are higher than those of the traditional detection device.