The experimental study of aluminum dust explosion pressure with three kinds of size under different ignition delay time was made in the self-designed horizontal pipeline dust exploding device by utilizing high voltage electrode ignition.The results show that: with the increasing of ignition delay time

the explosion pressure and the rate of pressure rise of aluminum dust first enlarge and then reduce;there exists an optimum ignition delay time to maximize the explosion pressure and the rate of explosion pressure rise of aluminum dust;the larger the aluminum dust size is

the more the optimum ignition delay time diminution is;and there exists an explosion delay time range which changes with the variation of the aluminum dust size.At last

experimental results is qualitative investigated in theory.