Abstract: Based on FEM (Finite Element Method) and CFD (Computational Fluid Dynamics), the effect of the number of damping plates and the distribution of damping orifice on the inner flow field and water spraying intensity distribution was studied. The water spraying intensity and it's deviation was compared among four kinds of headers, such as the header without damping plates, the header with one symmetric damping plate, the header with two symmetric damping plates, and the header with one non-symmetric damping plate. The result shows that the relative deviation of water spraying intensity of the header with two symmetric damping plates is the least one.