Abstract: Based on the N-S equations and the k-ε turbulence model, different kinds of UO₂ kernel reduction furnace equipments in PBMR, South Africa and INET, China were numerically simulated using computational fluid dynamics method. The simulation results show that these two kinds of furnace designs can not be achieved on the uniform distribution of gas flow in the axial direction, but show large volume at the top and small volume at the bottom of the furnace, and this is one of the reasons of non-uniform particle reduction. Improved design was proposed based on the analysis of changes of axial pressure in the furnace. Simulation results demonstrate that the improved furnace design is suitable for obtaining a more uniform distribution of the gas in the axial direction. It can be concluded that the improved furnace design will improve particle reduction effects.