Multichannel ultra-wide-angle polarimetric camera is a fine solution for polarimetric remote sensing by achieving multispectral, multiangle, and polarimetric information in target detection. By analyzing the optical system of Directional Polarimetric Camera, which belongs to this type, it is shown that the different aspects of the polarization properties of ultra-wide-angle lens (linear diattenuation and retardance) bring different effects on radiometric and polarimetric accuracies so that they can hardly be satisfied simultaneously. Based on the original design of Directional Polarimetric Camera, a method, which includes improved lens design, better optical coating design and modified polarimetric calibration is developed, to satisfy the accuracy specifications. After comparison between these two designs, the result shows that the improved method reduces the above so-called difference effectively. The method can work as a reference for accuracy design of other multichannel ultra-wide-angle polarimetric cameras.