The invention provides a high-precision grating positioning device directly driven by a limited angle motor, which comprises a motor drive circuit, a limited angle motor, a holographic diffraction grating, a photoelectric encoder, an interpolation circuit and a feedback control circuit. The rotor on one side of the limited angle motor passes directly through the bottom of the diffraction grating, while ensuring the center of the grating is located on the shaft, the stator is fixed on the outer heat dissipation frame, the motor is connected with the load through rigid coupling and directly drives the grating to rotate; the photoelectric encoder detects the angular position of the diffraction grating, and the output terminal of the photoelectric encoder is connected with the interpolation circuit. The interpolation circuit amplifies the sine and cosine signals outputted by the photoelectric encoder, doubles the frequency and interpolates after conversion, and connects the feedback control circuit through the interpolated output signal; the feedback control circuit achieves double closed-loop control of current feedback and position feedback, and the motor drives the circuit to generate the drive voltage to control the motor rotation. The high-precision grating positioning device has strong anti-interference ability, high resolution precision, and strong practicability and versatility.