Abstract: The morphology of MoO₂ and Mo powders prepared by the two-stage hydrogen reduction experiment of the spherical molybdenum trioxide powders was studied. The results show that, the spherical molybdenum trioxide (β-MoO₃) is transformed into α-MoO₃ firstly, and then the square γ-Mo₄O₁₁ is regenerated to form α-MoO₂ in first stage hydrogen reduction; Molybdenum powders are obtained in second stage hydrogen reduction. The morphology of MoO₂ is greatly affected by the reduction temperature and reduction atmosphere, the MoO₂ powders with fine and loose irregular morphology are obtained at low reduction temperature or by importing the water vapor into the reduction atmosphere; the MoO₂ powders with flake and hardened are formed at the higher reduction temperature or in the dry hydrogen with large flow. The morphology of ultrafine Mo powders is mainly affected by the reduction temperature, the water vapor partial pressure, and the hydrogen partial pressure. When the reduction temperature is low or the hydrogen flow rate is small, the ratio of the water vapor partial pressure and the hydrogen partial pressure should be close to the equilibrium constant as far as possible, and the uniform and dispersed ultra-fine molybdenum powders can be obtained.