Abstract: In order to reduce the loss of cotton in the separation process, the suspending velocity 2.6 and 0.8 m/s of the two kinds of materials were obtained through calculating and experiment . The velocity distribution in the key region was analysed using the Fluent software, as the inlet wind velocity set at 3.5, 4.0, 4.5, 5.0 m/s, respectively. The result indicated that under the condition of 4.0 m/s inlet wind velocity, the velocity content was 85%-86% during 0.8-2.6 m/s, which was the most according with the demand. The result indicated that both the experimental results and the simulative results were very similar. This study provides reference for further focusing on optimizing and designing the separator.