The metal coating material of Ag and dielectric thin film materials such as Ta2O5, SiO2 and Al2O3 are selected for designing and fabricating a kind of polarization-maintaining mirror on the quartz substrate, whose polarization contrasts at wavelengths of 810 nm and 850 nm are superior to 10000∶1. With the combination of the orbital environment for the polarization-maintaining mirror, the experiment for simulating the spatial atomic oxygen is conducted and the change law of polarization contrast of the polarization-maintaining mirror sample is investigated. The results show that, with the increase of the dose of the atomic oxygen, the polarization contrast of the polarization-maintaining mirror shows an overall decreasing trend. Moreover, the decreasing trends along the directions of +45° and -45° are more obvious than those along the horizontal (H) and vertical (V) directions.