Numerical calculation on fluid-structure coupling vibration responses of a reservoir-pipe-valve (RPV) system was carried out by the method of characteristics (MOC), the influences of pipe structure-damping, pipe Poisson’s Ratio and pipe wall thickness on vibration responses of the RPV system were studied. The numerical results show that the axial vibration energy of pipe wall is weakened with the increase of pipe wall damping, when pipe wall damping is greater a certain value, the vibration energy of the system mostly concentrates on fluid which enhances fluid pressure energy; pressure energy of fluid is enhanced meanwhile the axial vibration energy of pipe wall is weakened with the increase of pipe wall Poisson’s Ratio or pipe wall thickness.