Abstract: Installing air surge tank in pressure water system is a new and economically efficient measure to prevent water hammer accident. The authors set a new type air surge tank in the long-distance water delivery system of pump, built experimental mode and its corresponding mathematic model, and made the theoretical analysis, numerical and experimental study on the models. Through the analysis, the mathematic model simulated by numerial value and its calculation programme is testified so as to provide the theoretical basis of applied air surge tank for the optimum design of power station and pump station, and provide the calculation software of water level fluctuation in air surge tank after pump power-off.