Abstract: The vibrational characteristics and the input power flow of a cylindrical shell filled with fluid are investigated.Based on Flugge's shell equations,the sound wave equation for the fluid field and the boundary condition at the fluid-structure interface,the dispersion equation for this coupled system is deduced.By using Fourier transforms,the equation of the vibrational power flow from a line circumferential cosine harmonic force is obtained.An integrate numerically method is used to calculate the result and the effect of an internal flow on the result is also discussed.