Abstract: The proton irradiation experiments with different energy were carried out on the new 8-transistor (8T) CMOS image sensors. As the total ionization dose (TID) effect and displacement damage dose (DDD) effect are caused simultaneously after proton irradiation, the degradation of device performance is more complicated. In order to specifically distinguish the main factor causing the degradation of different parameters, the equivalent TID method and equivalent DDD method were adopted. It is concluded that DDD mainly causes the degradation of dark current, while TID mainly causes the degradation of spectral responsivity, which has a guiding effect on the hardening design of image sensor in the irradiation environment.