Based on the AlGaN photocathode solar-blind UV image intensifier developed by the Science and Technology on Low-Light-Level Night Vision Laboratory, this study designs a UV optical system that matches the solar-blind UV image intensifier to improve the detection performance of the detector. The working wavelength of the optical system is 240.280 nm, the field of view is 40°, and the relative aperture is 1/2.5. The system consists of five lenses that are all spherical mirrors, and the total length of the optical system is 50.74 mm. When the optical transfer function is 40 lp/mm, the on- and off-axes are greater than or equal to 0.8 and 0.6, respectively. The imaging quality is good, and the structure is compact to meet the design requirements.