The steam-assisted gravity drainage (SAGD) process is effective to improve oil recovery performance, but it also promotes the aquathermolysis reaction of heavy oil under high-temperature reservoir environment. In the present work, a geological model considering core-catalyzed aquathermolysis was established and used to simulate mining in the SAGD process. Results showed that gas generation from aquathermolysis reaction was enhanced by core. Then, the gas production model considering aquathermolysis catalyzed by core was embedded into the geological model. The simulation results show that the main reaction areas of aquathermolysis occurred at the top of the reservoir and the liquid pool near the production well. The steam chamber growth was suppressed, and the simulation results of oil production and cumulative steam-oil ratio were closer to the actual recovery date. By adopting the new model, the recovery situation can be predicted more accurately, so that we can determine the impact of different harvest conditions on the SAGD process.