Abstract: In order to improve the reflectance of the GaSb-based laser cavity mask, the laser cavity film was designed in accordance with the relevant film design theory and by film-design software. The reflectance of the high anti-reflection film was higher than 95% in the band of 2-3.5 m; the transmittance of the antireflective film was higher than 99% at the wavelength of 2.5 m. The theoretical and experimental reflectance curves of high reflector and the single layer antireflection coating were compared through repeated experiments. Though the experimental results did not reach the theoretical value, they could meet the requirements of the application. The selection of the film materials was discussed by comparison of various material properties.