Combination mode and working parameters of the cleaning fans of the combine harvester have an important influence on the loss rate and the cleaning rate for different cleaning materials. In this paper, when centrifugal fan was acting alone and cross-flow fan acting alone, the airflow velocity at the indoor space point of cleaning room were measured on a cleaning device. The isokinetic distribution diagrams in different sections were drawn and the characteristics were analyzed. The results showed that under the action of the centrifugal fan, the airflow speed increases as the speed increases. The influence of the cross-flow fan on the screen surface is mainly concentrated on the screen tail, the increase in the speed of the cross-flow fan will expand the scope of influence.