A ground-based polarization-Mie lidar has been developed to measure backscattering signals from the atmosphere and linear depolarization ratios at 532 nm. To retrieve depolarization properties of clouds and aerosols, the calibration factor of two polarization channels at 532 nm must be calculated. Three different experimental methods are presented to determine the calibration factor in this polarization-Mie lidar. Some measured examples are presented and discussed. Experimental and CALIPSO results indicate that these methods are feasible.