A one-dimensional mathematic model is presented which describes pressure fluctuations behavior of liquid-filled pipes. The model is based on conventional two-equations water hammer theory. Here is multi-water-hammer occurring simultaneously and coupling together. The differences are obvious when taking into account coupled water hammer and just single water hammer in Fluid pipe system by comparing the numerical simulation. The pressure characteristics located where water hammer takes place is investigated by numerical simulation and experiment. Then the factors of influencing on the coupled water-hammer pressure and frequency are considered, the result shows that system parameters effecting on it are critical and should be detailedly analyzed.