Abstract: To investigate the effects produced by a stiffened cylindrical shell indentation on underwater vibration and acoustic radiation，an approach combining the finite element and boundary element was adopted. Through FORTRAN and DMAP codes，the added mass and added damping matrices were first computed，and then added to the structural mass and damping matrices，where the problem of fluid structural interaction was solved. The corresponding frequency response curve measuring the mean-square velocity and radiated sound power from cylindrical shells with different sizes，depths，positions of indentation were obtained. The results show that when the force point deviates from the position of indentation，the indentation has little influence on underwater vibration and acoustic radiation. On the other hand，when the force point locates at the same position as the indentation，the decibels of mean-square velocity and radiated sound power appear to be significantly higher（up to 4 dB）than that those under the condition without indentations. Therefore，it is advisable to avert forces from positions of indentation when conducting experiments on vibration and sound radiation from cylindrical shells.