Wind-blown sand has an important effect on plant physiological processes, but there is no any theoretical model to explain its mechanism.Based on the rigid conduit model of the plant stem, this paper discusses the effect of wind-sand electrostatic field on the speed of plant sap flow.The numerical result shows that with the increasing of external electric field, the sap flow rate corresponding exponentially increases, accordingly the stronger external electric field, the faster the water transport; with the increasing of conduit radius, the water transport rate increases, and the effect of environment electric field on plant sap flow is more obvious.To some extent, these results can explain why the effect of wind-blown sand on plant is larger than that of the net wind, and it will provide some helps for the vegetation protection on arid areas.