Abstract: To study the winnowing process of tobacco products from threshing in a centrifugal pneumatic separating chamber, the movement of and force acting on the tobacco products in the separating chamber at different inlet air velocities were analyzed based on CFD-DEM coupling method. The simulation results showed that with the increase of the inlet air velocity, the pressure in the chamber increased gradually, the impaction between the tobacco products raised, however the uniformity of the flow field changed insignificantly. At the inlet air velocities of 11, 13, 15 m/s, the maximum impacting forces between tobacco strips and separating chamber were 0.155, 0.164, 0.378 N and the corresponding stem content in strips were 2.46%, 2.37%, 3.12% respectively. An experiment was carried out by taking the stem content in strips as the criteria for evaluating the efficiency of pneumatic separation, and the results indicated that when the inlet air velocity was 11, 13 and 15 m/s, the stem content in strips was 2.27%, 1.84% and 2.54% respectively. The error between the simulation results and the experimental results was less than 1 percentage point, which verified the rationality of the simulation. This study provides a theoretical support for optimizing the structure and technical parameters of pneumatic separating chamber.