Based on Bi_1.5Sb_0.5Te_1.8Se_1.2 material, a grating-type ultraviolet absorber was designed. Using the finite element method, the dependence of the absorption characteristics of the absorber on structural parameters, incident angle and working wavelength was analyzed in detail. The absorption mechanism of the absorber is the magnetic polariton resonance effect. By adjusting the structural parameters, incident angle and working wavelength, the absorption characteristics of the absorber can be adjusted. With optimized parameters, the absorption rate can reach more than 80% in the wavelength range of 200~400 nm and the incident angle range of 0~75°. The work in this paper provides a theoretical basis for the design and manufacture of ultraviolet absorbers and their applications in ultraviolet detection and protection, biosensing, and ultraviolet photocatalysis.