This study aims to predict the severity of coal dust explosion in confined space and to provide guidance for effective suppression of explosion. Based on kinetic analysis of devolatilization and heat transfer mechanism of inert particle-coal particle-pyrolysis gas in confined space, a mathematical model for suppressing coal dust explosion by inert powder was established. Compared with the experimental results of 20 L spherical explosion tank, relative errors of the maximum explosion pressure (P-max) and the maximum rise rate of explosion pressure ((dP/dt)(max)) predicted by the model were both < 0.15. The particle size of inert powder was concentrated in 0.1-10.0 pm, while 90 vol% coal particle was in the size range of 0-23 mu m. The convective of pyrolysis gas and coal was weaker than the radiation of coal and inert particle. When the proportion of inert suppressant increased to 50 wt%, (dP/dt)(max) was reduced from 50.14 MPa/s of raw coal to 6.70 MPa/s, and P-max was reduced from 0.78 MPa of raw coal to 0.16 MPa, which basically achieved the complete suppression of explosion. Due to the difference in inherent composition of coal, the P-max and (dP/dt)(max) of ZT lignite were higher than that of SM bituminite. This study can provide a basic reference for the severity of coal dust explosion and suppression prediction in industry.