Abstract: The polarization effect is inevitable when light-splitting film is titled. Any effective measures were usually taken to reduce the influence of polarization effect, but only single wavelength or very narrow spectral range can realize non-polarizing, the spectral range was almost no more than 50 nm. An initial formula was designed by resolution method according to the design target, Then, the incidence of angle with 45 light-splitting film from 1260 nm to 1360 nm spectral range was designed by resolution, needle and variable metric optimization methods on the designed initial formula by using TFCalc formula design software. The monitoring transmittance curve of designed formula was analysed to decide whether it could be deposited. The formula was deposited by the type APS1104 deposition machine made in Germany, light-splitting film with good performance was acquired.