Based on the theory of optical thin film and the characteristics of optical materials, by combining with the film system design software and using the principle of splitting technique, the design of double-sided film system is achieved, which solves the problem that the single-sided thin film is too thick and with an excessive stress. With the inverse analysis method, the experimental test results are inversed. With the research of the sensitivity distribution of film layer, the causes of the errors are analyzed, and the thickness of sensitive layers of film system is precisely controlled with different monitoring methods. The final spectral test results of prepared filter films show that the transmissivity of single point is 93.7% at the wavelength of 3.31 μm, the full width of passband at half maximum is 49 nm, and the mean transmissivity at wavebands of 1~3.2 μm and 3.4~5 μm is 0.17% , which can meet the operational requirements of the system.