To solve the problem of calibrating the polarimeter module, a new approach based on vector projection algorithm was proposed, and the principle of calibration was analyzed. The continuous-wave (CW) light passed through the tunable optical attenuator, polarization analyzer, photon detectors of polarimeter module, then the photocurrent was fed into the preamplifier circuit and high-speed analog to digital converter (ADC) in turn. Finally, the digital voltage signals were acquired by the digital signal processor (DSP) and sent to the computer. At the same time, the polarization analyzer exported corresponding Stokes parameters. The calibration matrix could be calculated by the vector projection algorithm based on the given data. The experimental result shows that, in comparison with the common iterative algorithm, the vector projection algorithm has even higher computational efficiency and accuracy. The measured error of the degree of polarization (DOP) is less than 3 percent.