Abstract: Ultrafine Mg powders were prepared by resistance heating evaporation and induction heating evaporation respectively.The effects of gas pressure on the productivity and granularity of the powders were systematically studied.The powder structure was analyzed by XRD,TEM and other analysis methods.The results show that the productivity of induction heating evaporation is larger than that of resistance heating evaporation.The productivity decreases and the mean particle size increases with increasing gas pressure.The ultrafine Mg powders are polymorphic,with a chain-ball structure and high purity,and the distribution of particle size is narrow.