The relative spectral respone is one of the basic parameters for detection and evaluation of the performance of the directional polarization camera. A set of devices to measure relative spectral response of the directional polarization camera was assembled, which consisted of laser pumping xenon light source monochromator, depolarizer, reference detector and 45° beam splitter. The synchronization measurement method of beam splitter was utilized to reduce the instability of the light source. On the basis of monochromator and data acquisition system developed by different development platforms, an automatic testing system for the relative spectral response was developed by using ActiveX and dynamic link library technology to solve problems of complex testing process and long testing time. This automatic testing system has reduced the impact of time stability, and improved accuracy and efficiency of the measurement. Taking 490 nm and 865 nm channel of the directional polarimetic camera as an example of application, the experiment of relative spectral response in instrumental level measurements was carried out. The experimental results showed that the accuracy of the ratio between measured range value of the center wavelength and the average value of the bandwidth of directional polarimetic camera is within 0.11%, which meets the responsivity non-uniformity calibration requirement of less than 0.6%.