Abstract: To investigate the impact of thermal effects (thermal stress caused by temperature field disturbances) induced by CO₂ injection into high-temperature reservoirs on fault activation, a geological formation located 800 meters underground in a mine in Inner Mongolia was taken as the research object. A two-dimensional thermo-hydro-mechanical (THM) coupled damage model considering injection temperature is established by numerical simulation. Three cases with CO₂ injection temperatures of 35 °C, 45 °C, and 55 °C were set to systematically analyze the variation laws of reservoir permeability, fault vertical displacement and pore pressure. Fault stability was comprehensively evaluated using fault shear slip tendency, safety factor and Coulomb stress parameters. The results show that when the injection temperature increases from 35 °C to 55 °C, the maximum horizontal radial distance of the CO₂ plume increases by about 14% after 50 days of injection, and the peak pore pressure in the fault zone decreases by about 16% during sequestration. When the injection temperature reaches 55 °C, the stabilizing effect generated by thermal effects is dominant, which can effectively inhibit fault activation. Fully considering the thermal effects of injected fluid in CO₂ geological sequestration projects is of great guiding significance for weakening the fault response induced by fluid injection and ensuring sequestration safety.