This paper described the preparation method for composing high-grade synthetic diamond by water atomizing using FeNi30 powder catalyst. The objective of this article is about powder making process using super high water atomizing in the atmosphere of inert gas, and then corroded the powder with a corrosion inhibitor. Finally, FeNi30 catalyst powder with lower oxygen content and good sphericity is produced. The experiment of making diamonds by using cubic press and the performance of the diamonds are also discussed.