Abstract: The typical water hammer theory is introduced at first,and the shortcoming of typical water hammer to calculate water hammer in the space pipe is analyzed,and then the CFD method to study the effect of water hammer in space pipe is applied.If the coupling effect of the structure and the fluid is not considered,the fluid govern equation in the space pipe can use the basic fluid control equation.The result can be obtained by CFD technology,when the govern equation and the fluid state equation and the initial condition,boundary condition is obtained.The numerical effect numerical dissipation and the frequency dissipation is avoid when the case include wave process.The CFD is applied to simulate the model in related reference,and discuss the effect of the discrete format and the grid.Finally the progress of the water hammer in the pipe is discussed.The method in this paper can be used in more complex pipe system to simulate the water hammer effect.