Abstract: The pre-reduction molybdenum powders containing minor amount of MoO₂ were prepared by the carbothermic reduction of MoO₃, using the carbon black as the reducing agent, then the obtained pre-reduction molybdenum powders were deep reduced by hydrogen to finally prepare the ultrafine molybdenum powders with the average particle size of 99 nm to 190 nm. The effects of the carbothermic reduction temperature on the particle size and the residual carbon content by mass of the ultrafine molybdenum powders were studied. In the results, with the increase of C/MoO₃ molar ratio from 2.0 to 2.1, the particle sizes of the ultrafine molybdenum powder products change little at the same reduction temperature. But the carbothermal reduction temperature shows a significant effect on the particle size and purity of products. When the C/MoO₃ molar ratio is 2.1, with the increase of reduction temperature from 950 ℃ to 1150 ℃, the average particle sizes of products increase from 100 nm to 190 nm, and the content of the residual carbon by mass decreases from 0.030% to 0.009% after the hydrogen reduction.