Abstract: Based on the basic principle of hydromechanics, the flow characteristic of drilling fluid on the screen was studied. By taking the consideration of various parameters affecting the screening effects, such as vibration and screen angle, a screening model for a drilling fluid shale shaker was established. The screening equations were solved by average energy principle and finite differential method, and the treating capacity of a shaker was calculated numerically. The comparison between the results of calculation and indoor simulation rig test shows that the screening model is of high accuracy.