A polarization calibration method based on adjustable polarization source is proposed, and the calibration and correction of measurement results of degree of linear polarization of spectropolarimeters based on polarization spectral intensity modulation (PSIM) technique are completed by using this method. The linearly polarized light with different degrees of polarization from the adjustable polarization source is used as the source to be measured, and the original data is obtained from the output of the source to be measured by the PSIM spectropolarimeter. The correction coefficient is obtained by linearly fitting the polarization degree spectrum obtained by analyzing the original data and the theoretical polarization degree spectrum output by the light source to be measured. The results of the PSIM spectropolarimeter were calibrated and corrected by using the coefficients. The results show that in the effective measuring band (500~650nm), the measurement accuracy of the PSIM spectropolarimeter is significantly improved after calibration and correction, and the maximum error between the PSIM and the output standard polarization degree decreases from 0.017 to about 0.003, which indicates that the polarization calibration and correction method based on the adjustable polarization degree source is feasible.