Experimental studies on the explosion venting of aluminum dust were conducted in 1.3 L Hartmann tube connected to a vent duct. The experimental results show that the maximum reduced pressure increases with relieving pressure increasing. In the contrast,the maximum rate of pressure rise decreases with relieving pressure increasing. Vent duct being wider， the maximum reduced pressure is lower. There exists an optimum concentration making the maximum reduced pressure and the maximum rate of pressure rise reach to a maximum. The concentration is higher than that of no duct venting. The effect of dust particle size on the maximum reduced pressure can be ignored，while the maximum rate of pressure rise increases with particle size decreasing. The higher pressure is measured in the condition of tube connected to a duct.