Abstract: Aluminum powder is an important mental industrial raw material, it is significant to prevent aluminum dusts explosion effectively. Explosion experiments were carried out for six micro-aluminum powders with different particle sizes in different concentrations by using 20 L spherical vessel to investigate the effects of aluminum dust concentration and particle size on explosion characteristics, and the explosion products were also analyzed. The results show: the maximum explosion pressure, the rate of pressure rise and explosion index all vary with dust concentration increasing, and their curves are parabola and reach the peak value in optimum concentration which is 500g/m³. The maximum explosion pressure and the rate of pressure rise both rise with aluminum dust particle size decreasing, and their curves are exponential. They increase rapidly when particle sizes less than 10μm. The combustion time in explosion of dust cloud decreases as aluminum dust concentration increasing, and gradually trends to flat, besides its curve is exponential. The combustion time of aluminum powders decreases with aluminum dust particle size decreasing.