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 fully 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 paper focuses on a 55nm manufacturing process Hg _1-xCd _xTe IRFPA sensor widely used in image sensors, using a 2×2 basic pixel unit model for large-format arrays and constructing a Geant4 simulation model. Simulations were conducted for different proton irradiation fluences, including 10 ¹⁰, 10 ¹¹, 10 ¹²and 10 ¹³cm ^-2. The results show the displacement damage under various fluences, including non-ionizing energy loss and displacement atom distribution and others. It was found that, at a proton cumulative fluence of 10 ¹³cm ^-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, the study provides a preliminary assessment of the damage conditions in the space environment based on simulation results. This research provides crucial data support for the space applications of future large-format Hg _1-xCd _xTe IRFPA image sensors.