The branch networks are widely applied to the water supply engineering of villages and small towns. The most economical network design was obtained by using the optimal design. Considering the two types of load both maximum load and transfer load of network, the linear programming model was presented to optimize branch network with water tower back of network, based on the relation of the hydraulic pressure and discharge of the parts in network. Assured demand for the pressure and discharge of network nodes, the dimensions of network, the lift of pump and the height of water tower were determined, thereby the optimal design of branch network with water tower back of network was obtained, based on the linear programming model.