Ammonia fuel engines face problems such as low combustion efficiency, ammonia escape, and high N2O emissions. However, natural gas reserves are abundant, and the combustion speed is fast. In order to explore whether the mixing of natural gas can promote the combustion of ammonia fuel, this article discusses the combustion and emission performance of ammonia/natural gas hybrid fuel engines through simulation research. The results indicate that mixing ammonia fuel with natural gas can greatly improve the combustion efficiency of ammonia in the cylinder. Appropriate natural gas can greatly improve the power and economic efficiency of engines. Although the N2O emissions of the engine have significantly decreased, the CO2 and NOx emissions of the engine have significantly increased, and the engine's overall emission performance has become worse. Considering the engine's overall performance, this article selects A50/N50 as the optimal mixture ratio for ammonia/natural gas. The article's research results have effectively improved the problems existing in ammonia engines, providing research direction and data support for the development of ammonia fuels.