Abstract: Optics is the key part of a spectrophotometer, which directly affects system performance and accuracy. With low cost, easy operation and simple maintenance, appropriate spectral range and resolution requirements as design target, comparison of some feasible design solutions, non-symmetrical Czerny-Turner structure based on plane diffraction gratings was proposed based on the operation principle of spectrophotometer and the theory of optical design. The optical system is simulated in Zemax software. The results show that the spectrometer's spectral rang is 400~800 nm, and the spectral resolution is better than 1 nm, Measuring wavelength interval of 1 nm system spherical aberration and coma makes control within the aberration tolerance, and the volume of the optical system is approximately 95 mm×90 mm×44 mm, Nondispersive direction through a cylindrical lens correction. A scanning grating cooled detector is used to reduce cost, very suitable for the needs of general users.