Complementary metal oxide semiconductor (CMOS) image sensor is susceptible to proton single event effect when being applied to space environment. Proton irradiation experiments with different energy values are carried out on a commercial FSI and BSI CMOS image sensors. The proton single event effect is analyzed by on-line testing, the maximum proton energy is 200 MeV, and the total fluence is 1010 particle/cm(2). The single-event transient bright spots of different shapes are observed in the pixel array. By extracting the deposition energy and size, the effects of different energy protons on transient bright spot characteristics are compared, and the transient bright spot characteristics between FSI and BSI are also compared. Finally, the energy deposition distribution of the transient bright spot generated by proton in CMOS image sensor pixel unit is predicted by comparing the simulation method with the experimental results. The simulation results verify that the decrease of PPD depletion region thickness and the thinning of epitaxial layer are the main factors leading the proton energy deposition distribution to shift leftward in BSI image sensor.Complementary metal oxide semiconductor (CMOS) image sensor is susceptible to proton single event effect when being applied to space environment. Proton irradiation experiments with different energy values are carried out on a commercial FSI and BSI CMOS image sensors. The proton single event effect is analyzed by on-line testing, the maximum proton energy is 200 MeV, and the total fluence is 1010 particle/cm(2). The single-event transient bright spots of different shapes are observed in the pixel array. By extracting the deposition energy and size, the effects of different energy protons on transient bright spot characteristics are compared, and the transient bright spot characteristics between FSI and BSI are also compared. Finally, the energy deposition distribution of the transient bright spot generated by proton in CMOS image sensor pixel unit is predicted by comparing the simulation method with the experimental results. The simulation results verify that the decrease of PPD depletion region thickness and the thinning of epitaxial layer are the main factors leading the proton energy deposition distribution to shift leftward in BSI image sensor.