Abstract: In order to efficiently design the parameters of the pumping down tool and to improve the pumping efficiency of PE screens, a study was conducted to investigate the effects of drilling fluid, drilling pipe and pumping down tool parameters on the driving force of pumping down tools by means of a CFD numerical simulation method based on the on-site operational conditions of CBM horizontal wells.It was shown that the fluid pressure at the pressurized ledge of pumping down tools was positive and the fluid pressure at the guiding surface was negative.In view of the opposite directions of the positive and negative force, their resultant force was the force to drive pumping down tools forward.The driving force on the pumping down tools increased by increasing the flow rate, viscosity and density of drilling fluid, but the effect of drilling fluid viscosity on driving force was much less than that of drilling fluid density and flow rate.The driving force on the pumping down tools decreased quickly at first and then slowly by increasing of the annular clearance between the drilling pipe and the pumping down tool, and decreased lineally by increasing the drainage orifice diameter.The effect of annular clearance on driving force was much more than that of drainage orifice diameter.Indoor investigation and field application indicated that the driving force produced by thispumping down tool was large enough to satisfy the field operation of PE screen completion.