High-energy protons in space can cause performance degradation and pixel anomalies in complementary metal oxide semiconductor （CMOS） image sensors （CISs），significantly affecting space object detection.To gain a deeper understanding of the random telegraph signal （RTS） pixel issues induced by high-energy protons in CISs，in this paper，some proton irradiation tests are carried out on space-grade CISs，combined with several room-temperature and high-temperature annealing tests.The generation patterns of the RTS pixels are obtained，and the mechanisms underlying the RTS pixel formation are analyzed.The results show that the dark signals of the RTS pixels caused by protons can fluctuate across up to nine levels.The higher the number of levels，the fewer the number of RTS pixels，but the more frequent the transitions of the dark signals between levels become.This study suggests that the fluctuations in RTS pixel dark signals originate from the variations in defect configurations，with phosphorus-vacancy （VP） defects playing a significant role in the formation of RTS pixels.The findings provide a basis for the radiation hardening and on-orbit maintenance of CISs.