At the simulation platform of DFQX-3 air-and-screen cleaning device, the velocity of flow at different positions of the vibration sieve surface was measured through the space-points. With the measurement, the velocity of flow in the surface is less than 4.81m/s which is low-speed airflow. We used Matlab to plot the isovel and velocity variation curve of the cross section, vertical section and horizontal section at different positions in the screen surface, and then analyzed the distribution rules of the velocity of flow on the screen surface of the air-and-screen cleaning device. The result shows that the velocity of flow is symmetric on both sides of the screen surface, and is close at both ends while complex in the middle.