Abstract: In order to study the influence of mean diameter (D3,2) on the explosibility of coal dust with and without methane gas,20 L spherical vessel is used to measure the explosive characteristics parameters,the influence of particle size dispersion σD on the explosion power of coal dust is studied,and the correlations between the values of D50,D4,3 and D3,2 and the explosibility coal dust are analyzed,the solid residues of coal dust explosion is collected and characterized by a scanning electron microscope inally,the mechanism of coal dust explosion with and without methane gas is discussed on basis of dust explosion experimental results and the microstructure analysis results of the explosion solid products.The experimental results show that Pmax and (dP/dt) max values of coal dust with the maximum σD (2.31) increase by 14.71% and 68.05% respectively compared to those with the minimum σD(1.49),which shows that particle size dispersion σD of coal dust can significantly affect its explosion performance ompared with D50 and D4,3 values,D3,2 can better illustrate the explosion characteristics of coal dust.Pex and (dP/dt)ex values of coal dust with the maximum D3,2(120 μm) increase by 33.33% and 83.33% respectively compared to those with the minimum D3,2 (2.5 μm),therefore,the influence of D3,2 on (dP/dt)ex are higher than that of Pex n the methane gas atmosphere,with the increase of D3,2,the (dP/dt)ex value of coal dust explosion decreases gradually.When the methane gas concentration low,D3,2 had little influence on Pex values,but when the methane gas concentration high,larger D3,2 result in smaller Pex values.Smaller D3,2 of coal particles led to faster combustion rate of coal particles and higher explosibility,and the residues of coal dust has greater breakage and more holes in their surfaces.The results illustrate the importance of σD and D3,2 values on evaluating the explosion hazard characterization of coal dust or combustible dust,which is of great significance to the prevention of gas and dust explosion in coal mines.