A polarimetric calibration method based on non-polarized light source was proposed to solve the problem of polarimetric calibration of the multi-channel polarimetric imager. Through the study of the interaction between polarized beam and optics, the vector radiative transfer model of multi-channel polarimetric imager was deduced and the calibrated parameters were determined. The key parameters such as absolute radiometric calibration coefficients of center viewing field, polarization degree of optical lenses and relative transmittance with system low frequency were calibrated based on the vector radiative transfer model by application of polarimetric effects of the system with non-polarized light source. By analyzing the calibration result, the Mueller matrix of full field of view was solved. Furthermore, the accuracy of polarimetric calibration on typical field of view was verified with a light source with variable polarization degrees. The results show that the polarimetric calibration method based on non-polarized light source can effectively improve the polarization calibration efficiency of multi-channel polarimetric imager with the measured error of polarization less than 1% and the target degree of polarization less than 20%, thus meeting the requirements of measurement accuracy of atmospheric aerosol.