Abstract: Ammonia, as a low-carbon co-firing fuel with promising application potential, has attracted increasing attention for application in coal-fired power plants. However, its influence on the explosion characteristics of pulverized coal remains unclear. To investigate the explosion behavior of an ammonia–coal mixture in a confined space, a 20 L spherical explosion vessel was employed. The effects of different ammonia blending ratios (0%-50%) on the explosion characteristics of pulverized coal were experimentally studied. Key parameters, including the maximum explosion pressure, maximum pressure rise rate, and explosion index, were systematically measured. Furthermore, the explosion suppression mechanism was analyzed in depth from the perspectives of chemical kinetics, thermodynamics, and flame propagation. The experimental results indicate that ammonia blending can effectively suppress the explosion intensity of pulverized coal. Under an excess air ratio of 0.3, as the ammonia blending ratio increased from 0% to 50%, the maximum explosion pressure decreased from 6.6 bar to 3.8 bar, the maximum pressure rise rate decreased from 191.5 bar/s to 88.4 bar/s, and the explosion index decreased from 52 bar·m/s to 24 bar·m/s. From the perspective of reaction kinetics, ammonia suppresses the explosion by consuming highly reactive radicals such as OH and H in the chain reactions and generating less reactive NH2 radicals. This process interrupts the chain reaction pathways, thereby reducing the reaction rate and heat release efficiency and weakening the explosion intensity. Thermodynamic analysis indicates that with increasing ammonia addition, the concentration of H2O, a combustion product with a high specific heat capacity, increases, while the number of moles of gas generated from pulverized coal combustion decreases. These combined effects lead to reductions in both the system temperature and the total gas moles, thereby decreasing the explosion pressure. When the ammonia blending ratio increased from 0% to 50%, the H2O concentration in the system increased from 1.2% to 12.8%, while the CO concentration decreased from 29.8% to 2.1%, and the system temperature decreased from 1165 K to 835 K. From the perspective of flame propagation, the intrinsically low laminar burning velocity of ammonia reduces the overall burning velocity of the mixture when blended, thereby significantly decreasing the explosion index and weakening the destructive potential of the explosion. These findings provide theoretical insights and supporting data for the safe application of ammonia-coal co-firing technology.