Near infrared spectrometer is an important optical analytical instrument and has important application. By setting the enter slit, middle slit and exist slit, a spectrometer with a single grating and dual channels based on quasi Littrow structure is built to detect near infrared spectrum with a high dynamic range and tunable resolution. The optical system is simulated by using Zemax software. Then, a near infrared spectrometer with wavelength from 600 nm to 1700 nm is set up, and the spectrometer is composed of the optical system, control and analysis system and detection system. The results show that the light passes through the plane grating twice with quasi Littrow angle, the spatial dispersion effect of exit light spot is eliminated and the size of exit light spot is reduced, and then the spectrum edge noise is effectively restrained and the intensity of stray light is reduced. The dynamic range of the spectrum is improved by using the self-developed high dynamic detect system that cooperates with optical system. After spectral calibrating and relative radiation calibrating, the narrow band laser source is detected by using the spectrometer. The highest spectral resolution of the spectrometer, that is full width at half maximum, is better than 0.05 nm, and the dynamic range of the recovery spectrum around the central wavelength with a tolerance of ±1 nm is better than 70 dB.