Abstract: By means of fundamentals of hydraulics, multi-equations of hydraulic computation are set up for irrigation systems with parallel pumps and low-pressure water transferring pipes. These equations not only includes the junction continuity equation, real loop energy equation and supposed loop energy equation, but also include the total energy equilibrium equation between pumps and water outlets. So the method is different from that for other pipe networks. On the basis of these equations, all unknown flow can be obtained.