Because of the size limit of the spectrometer, the resolution of the micro-spectrometer is usually difficultly less than 0.1 nm when it meets certain spectral range. While some special applications require that the spectrometer not only has small size, but also requires extremely high spectral resolution. We used Zemax (optical design software) to choose the initial structure parameters and evaluation function to automatically optimize angle and distance of focus lens, cylindrical lens and CCD to design an optical system of spectrometer of Czerny-Turner structure. Its resolution is better than 0.05 nm, and the volume of the system is 90 mm×130 mm×40 mm. On this basis, eight grating slanting angles were optimized, and the spectral resolution of the micro-spectrometer is better than 0.05 nm, while the band range reaches 820 nm～980 nm. So the spectrometer has the characteristics of high resolution, wide spectrum and small volume.