The in-band relative spectral responsivity is a basic parameter for the detection and evaluation of the in-band response non-uniformity of a polarization remote sensor. A set of devices to measure the relative spectral responsivity of the polarization remote sensor is assembled, which consists of a laser pumping xenon light source monochromator, a depolarizer, a reference detector and a 45° beam splitter. The depolarizer is utilized to eliminate the output polarization characteristics of the monochromator, and the spectro-polarimetric analyzer (SPOLA) is utilized to measure and verify the depolarization accuracy. The synchronization measurement method of beam splitter is utilized to reduce the instability of the light source and to improve the measurement accuracy and efficiency. By taking 490 nm and 870 nm polarization channel of the atmospheric corrector as an example of application, the experiment of in-band relative spectral responsivity in instrumental level measurements is carried out. The experimental results show that the accuracy of the ratio between measured range value of the center wavelength and the average value of the bandwidth for atmospheric corrector is within 0.25%, which meets the in-band responsivity non-uniformity calibration requirement of less than 0.6%.