Abstract: The characteristics of vibrational power flow in an infinite elastic cylindrical shell filled with fluid are investigated. The simple harmonic motion of shell and the pressure field in the contained fluid are described by the Flügge shell equations and the Helmholtz equation respectively. The vibrational equation of this system is obtained by using the coupling of shell and fluid. By using the Fourier transform and its inverse transform, the input power into this coupled system under a simple harmonic,linearly distributed driving force is studied. Along the shell, the transmission of the power flow carried by different shell internal forces and by the contained fluid are discussed.