To investigate the effect of Mg content on the properties of centrifugal atomized aluminum-magnesium （Al-Mg） alloy powders， Al-Mg alloy powders with different mass ratios （70∶30， 50∶50， 30∶70） were prepared by centrifugal atomization. The particle size， morphology， physical phase， and kinetics parameters of the samples were characterized via the particle size distribution meter， scanning electron microscope （SEM）， X-ray powder diffractometer （XRD） and TG-DSC. The effect of different Mg content on the activity of the alloy was also studied by thermal oxidation at 71 ℃. Results showed that all Al-Mg alloy powders had a good size distribution， regular morphology and high sphericity. The metallographic structure demonstrated that Al-Mg30 and Al-Mg50 had a dendritic structure， and Al-Mg70 was composed of α-solid solution and dendritic precipitates. The main phase of the alloy was α-Al， β-Al₃Mg₂ and γ-Al₁₂Mg₁₇. The β-Al₃Mg₂ phase gradually decreased and the γ-Al₁₂Mg₁₇ phase increased with the increasement of Mg content. Moreover， the deactivation rate of Al-Mg alloy powders was found to increase with the increasement of Mg content. The activity of alloy powders remained basically constant after 48 h. The TG-DSC results indicated that both the initial exothermic temperature and the activation energy of the alloys were gradually reduced as the Mg content increased， but the reactive speed was accelerated. The increasement ratio of weight of all Al-Mg alloys was greater than that of micron Mg （53.06%） and Al （8.63%）. The results of Laser ignition showed that the ignition delay of Al-Mg alloy was much shorter than monolithic aluminum， as well as the combustion duration. The microburst phenomenon was observed in the test.