Abstract: Complementary metal oxide semiconductor (CMOS) image sensors have great application potential in space environments because of its small size, low power consumption, high integration and other advantages. In the space radiation environment, the electrical performance of devices will degrade due to the displacement damage effect caused by energetic particles, which in turn affects the reliability and stability of the spacecraft. Aiming at the problem of image sensor’s electrical property degradation in space radiation environment, Monte Carlo method was adopted to establish a geometric model based on CMOS APS device in this paper. Then the research on the interaction process between different energy protons and target atoms was conducted, and the type and number of primary knockon atom (PKA) generated by different energy protons in the depletion zone were calculated by binary collision approximation method. By comparing the PKA energy spectra and the mean displacement damage energy at different depths for various energy of incident protons, the discrepancy of displacement damage under various energy incident protons and space station orbit proton energy spectrum was analyzed. The result shows that the PKA energy spectrum is basically the same when the incident proton energy is greater than 30 MeV. The difference is that as the incident proton energy increases, the maximum energy of PKA and the contribution to the displacement damage energy from PKA produced by nuclear reaction gradually increase. For proton with energy greater than 1 MeV, the oxide layer in CMOS APS device has so little effect on displacement damage that it can be ignored. The result of the displacement damage energy deposition distribution in the device under different energy of incident proton and space station orbit proton energy spectrum by CREME96 model shows that, the total displacement damage energy in depletion region calculated from the space station orbit proton energy spectrum is approximately equal to the total displacement damage energy produced by the single energy 3.5 MeV proton incidence. This study provides a theoretical simulation reference for the selection of the proton energy in the experimental study of the dark current growth of electronic device in the space station orbit proton energy spectrum, and the energy spectrum distribution provides input parameters for molecular dynamics simulation calculations, which can further simulate the defect caused by cascade collision at the atomic level.