In order to verify the polarization and radiation calibration precision of the directional polarization camera (DPC) under natural targets, a verification experiment of measurement precision is designed. The data of the degree of polarization and radiation luminance for sky are obtained by imaging the sky in a clear weather and these data are compared with the simultaneous observation data by the CE318 sun-sky radiometer. The results show that, the average difference of the degree of polarization for the three polarization bands is smaller than 0.02, which meets the requirements of the polarization measurement precision of DPC, but the radiation luminance difference is big. After the correction of system deviation, the effect of the spectral non-matching between the calibration light source and target, and the effect of the inconsistency of the observation waveband and the observation visual field of two instruments, the average difference of radiation luminance for 490 nm and 670 nm channels of two instruments is less than 1%, and for the 865 nm channel is less than 2%, which verifies the validity of calibration data of DPC and the measurement precision of instruments.