Charge-Coupled Devices(CCD) is an image sensor used for visible light imaging in space photoelectric systems. For the ground simulation test of the space radiation effect of CCD, it is necessary to use appropriate bias conditions to analyze the space radiation damage of CCD. Because CCD is very sensitive to the total ionizing dose effect and displacement effect, it is of great significance to study the radiation effect and damage mechanism of CCD under different bias conditions because of the threat of the damaging effect faced by CCD space application. In this paper, γ-ray, and proton irradiation experiments are carried out on a buried channel CCD device under different bias conditions. The degradation rules of the total ionizing dose and displacement damage about radiation-sensitive parameters such as dark current and spectral response of CCD are obtained; as well as the damage mechanism of irradiation bias on the radiation effect of CCD. The results show that the bias of CCD under γ-ray irradiation has an important effect, but there is no obvious effect under proton irradiation. Meanwhile, the radiation damage mechanism of CCD is analyzed according to the structure of CCD and the results of the annealing test after irradiation.