Based on the polarization of skylight, the polarized light celestial positioning will have great application value when it has little position error. According to skylight polarization detection modle and single body celestial positioning modle, the polarized light celestial positioning error modle was built. Based on this model, the sensitivity of skylight polarization angle and sun direction was given, and the precision of polarized light celestial positioning was calculated. Analyzing results show that: 1)polarized light celestial positioning result will be better if the polarized direction detected on ship changes faster，so the detecting sensor can be set in the right direction according to the course, sun′s height and orientation; 2)the precision of polarized light celestial positioning system can reach NM level when the detecting precision of polarization angle achieves angle cent level.