Response characteristic of photodetector, which is caused by polarization state of incident light, is analyzed. The calculation formula of polarization-dependent sensitivity is deduced, and an InGaAs detector is fabricated for the experimental test. In order to test the polarization-dependent sensitivity of photodetector, an experimental system is established, and the polarization-dependent sensitivity of the InGaAs detector is measured. The results indicate that the experimental system has a good stability and the polarization-dependent sensitivity of the InGaAs detector is 0.27 dB under normal incidence，while 0.41 dB under 10° oblique incidence.