The polarization sensitivity is an important factor of quantification of remote sensing information, which is used to evaluate polarization response of remote sensors. In this paper, the white light laser, polarizing film, and the beam expander system make up the polarization measurement system. And then the polarization test is accomplished. Unlike the traditional analysis, this paper proposed a method of Fourier series fitting to analyze the polarization test data. Compared with the cosine function fit, Fourier series fitting is closer to the real data, and the influence of natural light and elliptic polarized light. And it has advantage in the error analysis of polarization test and can help improve polarization test precision. At last, the errors of polarization measurement is analyzed.