A large-format, high-resolution Hg_1–xCd_xTe infrared focal plane array (IRFPA) image sensor can be used in aerospace remote sensing and high-precision satellite imaging. The next generation of meteorological satellites in China will all adopt this type of image sensor. However, space high-energy protons can cause displacement damage effects in Hg_1–xCd_xTe IRFPA detectors and induce total ionizing dose (TID) effects in the pixel unit metal-oxide-semiconductor (MOS) transistors. This study focuses on a 55nm manufacturing process Hg_1–xCd_xTe IRFPA sensor widely used in image sensors by using a 2 pixel×2 pixel basic pixel unit model for large-format arrays and constructing a Geant4 simulation model. Simulations are conducted for different proton irradiation fluences, including 10¹⁰, 10¹¹, 10¹² and 10¹³ cm^–2. The results show the displacement damage under various fluences, including non-ionizing energy loss and displacement atom distribution. It is found that at a proton cumulative fluence of 10¹³ cm^–2, in addition to considering the displacement damage effect in the Hg_1–xCd_xTe IRFPA sensor, attention must also be paid to the TID effects on the MOS transistors in the pixel units. Additionally, this study provides a preliminary assessment of the damage conditions in the space environment based on simulation results. This study provides crucial data for supporting the space applications of future large-format Hg_1–xCd_xTe IRFPA image sensors.