The combustion process of pulverized magnesium particle cloud in powdered fuel ramjet preburner was studied and a one-dimension premixed laminar combustion model of pulverized magnesium particle cloud was established. The study shows that the laminar flame propagation of pulverized magnesium particle cloud is very stable, and the flame structure is almost invariable in the combustion process; the combustion zone thickness is very thin and the preheat zone thickness is about 2-3 times as much as the former. The magnesium particles vaporization and the homogeneous reaction of magnesium vapor and oxygen in particle cloud is the direct cause of flame and the key of flame propagation that; the preheat zone gas temperature rising depends mainly on the thermal conductivity of the combustion zone and the reaction heat of magnesium vapor which diffuses from combustion zone and oxygen while the preheat zone particle temperature rise depends on the convective heat transfer from gas phase to particle phase mostly. The effects of the interior parameters on the combustion of the magnesium particle cloud were analyzed. The effect of particle relative concentration on combustion of particle cloud is complex. When the particle relative concentration is low, increasing particle relative concentration is helpful for speeding up the particle cloud combustion process; when the particle relative concentration is high, increasing particle relative concentration is adverse to speeding up the particle cloud combustion process. With the increase of the particle size, the flame propagation speed is reduced, the flame temperature increases, and the thickness of preheat zone increases as well. With the increase of the initial temperature of particle cloud, flame propagation speed and flame temperature display linear growth, and the preheat zone thickness shows parabolic growth. The tendencies obtained by numerical simulation coincide well with those of the experimental results from the previous literature.