In this paper, the reason why the performance of space blackbody calibration systems are changed is analyzed. The space blackbody calibration system is exposed to the orbital vacuum and thermal environment, so its optical surface is easy to be contaminated by the contaminant sources in space. An analysis model for describing the damage of the blackbody calibration system due to contamination is established and the contamination influence parameters of the blackbody calibration system are calculated preliminarily. By sorting the space pollution sources, the affection of inner or external sources on the space blackbody calibration system is discussed and some suggestions on protecting the space blackbody calibration system are offered.