Radiation effects on complementary metal-oxide-semiconductor (CMOS) active pixel sensors (APS) induced by proton and gamma-ray are presented. The samples are manufactured with the standards of 0.35 mu m CMOS technology. Two samples have been irradiated un-biased by 23 MeV protons with fluences of 1.43 x 10(11) protons/cm(2) and 2.14 x 10(11) protons/cm(2), respectively, while another sample has been exposed un-biased to 65 krad(Si) Co-60 gamma-ray. The influences of radiation on the dark current, fixed-pattern noise under illumination, quantum efficiency, and conversion gain of the samples are investigated. The dark current, which increases drastically, is obtained by the theory based on thermal generation and the trap induced upon the irradiation. Both gamma-ray and proton irradiation increase the non-uniformity of the signal, but the non-uniformity induced by protons is even worse. The degradation mechanisms of CMOS APS image sensors are analyzed, especially for the interaction induced by proton displacement damage and total ion dose (TID) damage.