A wide band high-reflection film with low polarization effect is optimized by using genetic algorithm, and the polarization aberration correction of the reflective telescope in different wave bands is realized. The polarization aberration function is used to analyze the influence of metal film and low polarization film on the polarization aberration of Cassegrain telescope. The simulation results show that the diattenuation aberration of the telescope coated with low polarization film is slightly smaller than that of the telescope coated with aluminum film, while the phase retardance aberration decreases obviously, which decreases by 1.13 °, 1.00 °and 0.68 °at the wavelength of 355, 532 and 1064 nm, respectively. Finally, the influence of the selected film on the depolarization parameter error in different wavebands and fields of view is calculated according to the relationship between the Mueller matrix of the telescope and the atmospheric depolarization parameters. The results show that the measurement accuracy of depolarization parameter after polarization aberration correction of telescope will be improved.