To improve the performance of instrument and the inversion of remote sensing data, we analyze the influence of instrument optical system films on polarization. The xenon lamp, collimation system, Brewster polarizer and ultraviolet spectrometer are used to build a set of polarization response testing system. P polarized light and S polarized light polarization response characteristics of the instrument are measured in the range from 200 nm to 320 nm ultraviolet wavelength band. The test result indicates that the instrument shows different polarization responses under P polarized and S polarized light irradiation. When the polarization is changing from S to P, the peak wavelength of ultraviolet spectrometer response changes from 290 nm to 275 nm. Meanwhile, the energy of ultraviolet spectrometer under double pieces diffuser reduces by 40%~75% in comparison with single piece diffuser; under single piece diffuser and double pieces diffuser, spectrometer polarization response values both get maximum at 265 nm wavelength, while under double pieces diffuser, the polarization response of spectrometer is closer to unit value, and the variation of response to different polarization states is reduced, which is more suitable for the calibration requirement of the synchrotron radiation source.