Reasonable selection of pipe diameter of long-distance pumping water conveyance project greatly affects the investment and operation costs. Using the costs present value method, taking into account of the different water delivery volumes during the initial and long-term operation periods, the different pump station operation plans, the different the pump work heads and water pump efficiencys, and the two-part electricity prices, the economic pipe diameter for of long-distance pumping water conveyance project was determined. The project in Shanxi was taken as an example, the costs present value calculation diameter determination processes of pipe diameter for 4 types of pipe diameter, i.e, DN450, DN500, DN600 and DN700, and the diameter determination processes of economic pipe diameter were introduced. It can provide references for the selection of economic pipe diameter of similar long-distance pumping water conveyance projects.