Abstract: In order to improve the accuracy of wavelength scanning of grating spectrometer, we designed a set of real-time feedback system for grating rotation situation and implemented the instrument with both high speed and high precision scanning. In the design of feedback structure, we applied the grating displacement measuring technology to feedback the displacement of the slider on sine bar, and utilized the computer for receiving and processing it . Contrast experiment shows that the instrument accuracy of wavelength scanning is 0.7 nm, after incorporating the feedback circuit, the wavelength scanning precision can reach 0.15 nm. Results indicate that after adding can the feedback structure of the grating rotation situation, the grating spectrometer satisfy the requirement of high precision scanning.