Abstract: In order to study the effect of the inhibitor on the combustion characteristics of coal, sodium citrate and ammonium polyphosphate were mixed to carry out the experimental study on the optimization of the compound inhibitor. The combustion behavior and blocking effect of the retarded coal sample were analyzed with a cone calorimeter at the thermal radiation intensity of 45 kW/m ². The results show that among the selected experimental ratios, when the mass ratio of sodium citrate to ammonium polyphosphate is 3∶1, the heat release rate and total heat release of coal combustion are significantly reduced, the smoke generation duration is effectively shortened, and the smoke generation is inhibited, reflecting excellent flame retardant and smoke suppression effects. In the combustion efficiency of coal, the fire performance index of the system is improved, and the fire growth index is reduced. The combustion of coal is effectively inhibited, showing a good synergistic effect of the compound inhibitor.