Due to its high sensitivity, low false alarm rate, small volume, light weight, simple configuration and without cooling system, solar-blind ultraviolet detecting system is widely used in guidance, communication etc., especially in missile warning. According to the application requirements, a solar-blind ultraviolet warning optical system with large field of view and large relative aperture was designed. Based on the requirements of working distance etc., optical system aperture and other parameters were analized. Combined with the actual situation, the optical system selection and difficulty analysis were carried out. Three methods were used to solve the problem of illumination uniformity, and the design results of solar blind ultraviolet optical system with large field of view and large relative aperture were given. It has fine image quality in working spectrum 0.255-0.275 μm. All elements were designed with sphere and used fused silica only, thus have loose tolerance and are convenient for manufacturing and alignment.