According to variable incidence angle demands of anti-reflective film in infrared detectors, the influence of incidence angle on coating polarization effect is analyzed. Many effective methods were usually taken to reduce the influence of polarization effect, but non-polarizing can only be realized for a single incidence angle or a very narrow spectral range. 3～5 μm infrared anti-reflective film is designed with gradient and needle optimization methods on the designed initial film stack formula by using TFCalc formula design software. The p and s polarized light transmittance curves of designed formula with incidence angle from 0° to 60° are analyzed, and the effect of changing the film thickness by 2% on the transmittance curve of the designed formula is simulated. In this way, the infrared non-polarizing anti-reflective film is successfully designed with wide range and wide incidence angle.