With the continuous development of modern optical testing technology, the requirement of image process technology is increasing. As the gray-scale level contains important information of image, changing gray levels of the image can make the image detail more clear. Using filter technology can form different gray levels. Based on the optical thin film theory and combined with thin film design software, the design of a 3~5 μm thick filter film with incident angle of 0°~60° is achieved by establishing film optimization evaluation function. And using vacuum deposition technology, the gray adjustment film is fabricated. Adding copper mesh over the molybdenum boat can solve the problem of surface defects caused by the unstable deposition rate of SiO. The experimental results are simulated using reverse analysis method. The sensitive layer thickness of film system can be controlled by adjusting the film monitoring method. The controlled deviation of film thickness is reduced. So that the spectral curve is smoothed. After tests, the prepared film meets the requirement of gray adjustment in the infrared image system, and passes the relevant environmental tests.