Abstract: Radiation damage causes the dark current random telegraph signal (DC-RTS) on CMOS image sensors used for space and nuclear applications. Several 0.18 μm CMOS image sensors were irradiated by distinct proton energy and gamma rays, and the characteristic parameters of DCRTS were analyzed after irradiation. Experimental results show that there are discrepancies between DCRTS pixels due to displacement damage and to total ionizing dose effects in terms of discrete level, maximum transition amplitude and average time. This is because both kinds of radiation damage induced RTS defects are different. Contrary to the DCRTS due to displacement damage, total ionizing dose induced DCRTS features small transition amplitude and low transition frequency, which gives rise to the test and analysis challenge for this DCRTS. Transfer gate voltage during integration has an important impact on total ionizing dose induced DCRTS. The above work provides an important reference for the better understanding of DCRTS phenomenon on CMOS image sensor, and the exploration of relevant suppression techniques.