Complementary metal-oxide-semiconductor (CMOS) image sensors can easily be susceptible to proton irradiation in space applications. A proton irradiation experiment of a domestic commercial CIS was conducted on the ground, and the cumulative radiation effect and single event effect were studied by using offline and online image acquisition methods. The proton-induced cumulative radiation effects were studied by analyzing the dark signal degradation after irradiation, and histogram and generation mechanism of dark signals were analyzed from the aspects of total dose and displacement damage. Online testing results show that proton-induced single event transients in active pixel array include transient bright spot, transient bright cluster, and transient bright line. The interaction mechanism of proton and CIS was analyzed to discuss the different single event transient phenomena. No single event latch-up and single event function interruption in the peripheral circuits of the CIS was observed in the experiments.