Abstract: High-speed mixed bed is the most common desalination equipment in condensate treatment system, which plays an important role in improving the water vapor quality of thermal system. In order to reveal the flow law within the water cushion layer of the high speed mixing bed and to clarify the influence of the flow rate and the height of the water cushion layer on the uniformity of water distribution in the high speed mixing bed, this paper adopts the numerical simulation with Gambit software to study the flow law within a spherical high speed mixing bed. The results show that the jet region formed at the outlet of the water cap gradually shrinks and attenuates within the water mat layer, spreads around in the upper part of the resin layer surface, and forms a countercurrent region in the wall area of the mixed bed. The flow resistance in the high-speed mixing bed mainly comes from the water cloth plate, and the resistance of the water cloth plate under the rated condition accounts for about 13.3% of the total resistance of the mixing bed. As the flow rate decreases from 870 t/h to 330 t/h, the relative velocity deviation within the water mat increases slightly, but the difference is not obvious, with a maximum difference of 6.45%. As the height of the water mat was reduced from 992 mm to 592 mm,the relative velocity deviation on the surface of the resin layer decreased from 0.236 to 0.079, indicating that the velocity distribution on the surface of the resin layer became more uniform. The results of this study can provide a reference for the optimization of the design of high-speed mixing bed structure.