Abstract: In the analysis of transient in long pipeline, it is veryimportant to compute the hydraulic friction as accurate as possible. Inthe past, in order to reduce the operations, the fixed viscous frictioncoefficient and first-order approximation were used to compute thefriction term in the basic equations of transient flow. But thistreatment is inadequate. In this paper, the treatment of the frictionterm by using friction coefficient varying with flow conditions and asecond-order integration is more accurate. At the same time, on thebasis of the theoretical analysis, the influence of hydraulic frictionto transient flow was studied.