Abstract: In order to study the influence of the particle diameter on the initial expansion energy of released gas,the initial expansion energy of released gas of coal sample with different particle diameters(0.5<～1,1<～2,2<～5,5<～10,10<～15 mm)in Ⅱ₂ coal seam of Xuehu Coal Mine was determined under the same temperature condition.The results show that the relationship between the initial expansion energy of released gas and the gas pressure is adequately described by the linear equation for every sample.There is negative exponential function between the initial expansion energy of released gas and the average particle diameter under the same gas pressure condition.The greater the average particle diameter is,the smaller the initial expansion energy of released gas is,and vice versa.Thus,after the destruction of ground stress for coal,the smaller the average particle diameter is,the higher the outburst risk is.The conclusions above prove that the outburst risk can be reduced by coal seam gas pressure relief and increasing the coal strength after solidifying.