The ignition-proof time of the magnesium powder with 0.2～1.0 mm in size prepared by electromagnetic vibration atomizing and quenching has been examined at 1 000 ℃.The results show that the ignition-proof time of rapidly-solidified magnesium powder keeps for 17～21s while that of milling-passivated magnesium powder keeps for 11～14 s.The morphology of the rapidly-solidified magnesium powder was observed by SEM and EPMA.It is found that the C-enrichment on the surface of the magnesium powder can be observed.The chemical stability of powder surface can be strengthened to lead to the passivation effects due to the formation of compact surface during rapid solidification.