In view of the problem of model establishment in the simulation analysis, the Multi Reference Frame model is selected. The reduction formula of the velocity between absolute reference frame and relative reference frame is determined. Factors influencing air mass flow and speed at sucking inlet are studied by changing rotating speed and the distance between material transport pipe and the roller. According to the results, the structure size and operation parameters are optimized. The results show that the Multi Reference Frame model can realize the flow field simulation analysis. For assignment width of 400mm, when the roll speed is 300rad/min and the distance between transport pipe and roller is 350mm, the air mass flow and speed at sucking inlet are the largest.