Abstract: The effects of total ionizing dose (TID) and displacement damage from proton irradiation on an 8transistor global shutter exposure CMOS image sensor (CIS) within a star sensor were presented to analyze the sources of star sensor performance degradation and the decrease of attitude measurement accuracy. The dark current, dark signal nonuniformity, and photon response nonuniformity versus the displacement damage dose (DDD) were investigated. The star diagonal distance accuracy, and star point centroid positioning accuracy of the star sensor versus the DDD were also analyzed. The influence of space radiation on star sensor performance parameter was analyzed innovatively from a system level point of view. This work lays the foundation for the research of star sensor attitude error measurement and correction technology, and also provides some theoretical basis for the design of highprecision star sensor.