In order to monitor the change of solar spectral irradiance with high accuracy, a high accuracy solar spectral irradiance monitor is designed to obtain solar spectral irradiance data. The instrument has three independent optical paths. The main light path is used to measure solar spectral irradiance, the reference light path is used for spectral calibration, and the solar tracking light path is used for precision solar tracking outdoors. The design of the main light path is introduced in detail. Féryprism is used for dispersion and convergence in the main light path, and the entrance slit of the monitor is imaged to the focal plane of the Féry prism. Two photodiodes are used to detect the spectral irradiance from 380 nm to 2500 nm by rotating the prism. Through theoretical analysis and experimental verification, it is shown that the full width at half maximum of the monitor is less than 40 nm in the 380～2500 nm spectral range. Standard lamps are used to verify the spectral response range of the solar spectral irradiance monitor, and the experimental results show that the spectral range of the monitor meets the measurement requirements.