The measurement accuracy is an important technical index of the Spaceborne Directional Polarimetric Camera which achieves multiangle polarimetric information in target detection. In order to research the elements affecting the measurement accuracy of the instrument, the polarized radiometric theoretical model of every single pixel of the instrument which contains parameters representing physical concept clearly is established in steps by using mathematical description called Stokes-Muller and analyzing characteristics of the instrumental optical structure. The theoretical measurement errors of Degree of Linear Polarization on a single pixel, introduced by some important parameter deviations of all the components in the instrument, is calculated and analyzed. The results shows that there might exsit proportional relationship between the theoretical measurement errors of Degree of Linear Polarization and the deviation of the relative transmission of the channels, the deviation of the high frequency part of the spatial variation of the transmission mainly due to the inter-pixel sensitivity variation, the deviation of the orientation of the polarizer, the deviation of the polarization rate of the optics. When the deviations of the parameters exist, the theoretical measurement errors of Degree of Linear Polarization affected by the different kinds of incident light are acquired. According to the measurement accuracy of the instrument, the tolerances of the parameters are proposed for the most sensitive kinds of incident lights by the way of equal distribution of the errors. The study provides a theoretical basis and practical guidance for the development, calibration and data post-processing of the Directional Polarimetric Camera.