Abstract: Secondary explosion experiments of coal dust were carried out by use of 20 L spherical explosion device under the conditions of different coal dust concentration, particle size and ignition energy separately, and influence of coal dust concentration, particle size and ignition energy on combustion duration and residual gas was analyzed. The results show that under the same conditions, the secondary explosion combustion duration(T2) of coal dust is greater than the first explosion combustion duration(T1). Ignition energy has the greatest influence on T2, and coal dust particle size has the least influence. With increase of coal dust concentration, T2 first decreases and then increases. With decrease of coal dust particle size or increase of ignition energy, T2 decreases continually. For the same kind of gas under the same conditions, volume fraction of residual gas after the secondary explosion of coal dust is smaller than that after the first explosion. In a certain range, with decreases of coal dust particle size, volume fraction of residual CO continuously decreases after the secondary explosion, ratio of volume fraction of CO to the one of CO2 decreases, and volume fraction of CH4 increases. With increase of ignition energy, volume fraction of residual CO or CH4 after the secondary explosion continuously increases, and ratio of volume fraction of CO to the one of CO2 shows an increasing trend.