Ultrafine zirconium powder was prepared by high purity sponge zirconium, high purity hydrogen deep hydrogenation and gradient dehydrogenation. The sponge zirconium is deeply hydrogenated with high-purity hydrogen at a certain temperature to produce zirconium hydride with low oxygen content, which is easy to be crushed into fine particles. The zirconium hydride reaches a certain particle size after high-energy ball milling, and then dehydrogenated at a gradient temperature to obtain ultra-fine zirconium powder. The processes of high purity hydrogen deep hydrogenation, high energy ball milling and gradient dehydrogenation in the production of ultrafine zirconium powder were briefly analyzed. The results show that the hydrogen content in zirconium decreases gradually with the increase of temperature. At 700 ℃, zirconium hydride appears endothermic peak and decomposes rapidly. The hydrogenation reaction of zirconium is 400 ~ 700 ℃ and the dehydrogenation reaction temperature is 600 ~ 800 ℃. For zirconium powder prepared from the same raw material, the lower the particle size of zirconia, the higher the oxygen content.