Abstract: A standard Godbert-Greenwald furnace apparatus was used to measure minimum ignition temperatures of magnesium dust cloud under different conditions. Experimental results reveal that corresponding minimum ignition temperatures of dust cloud for four magnesium specimens with the medium grain diameters D50 of 6, 47, 104 and 173 m are 480,520,620,700℃, respectively. Take the magnesium powder with the grain diameter of 6 m for example, under the constant diffusing pressure of 0.1 MPa, the minimum ignition temperature of the magnesium dust cloud decreases from 600 ℃ to 480 ℃ corresponding to the dust concentration changing from 424 g/m3 to 5 085 g/m3; and for the constant dust mass of 0.3 g, when the diffusing pressure increase from 0.1 MPa to 0.2 MPa, the minimum ignition temperature of this magnesium dust cloud increases from 540 ℃ to 580 ℃. And effects of grain diameter distribution, concentration and diffusing pressure on the minimum ignition temperature of magnesium dust cloud were analyzed by the above experimental results. It is helpful in the explosion-proof equipment design for the magnesium powder production.