Abstract: The numerical calculation of underwater structure＇s acoustic radiated field has been carried out with the FEM and I-FEM. At first, the vibration acoustic model was built by ANSYS and the fluid-structural coupled vibration in time domain was also calculated. Data file for acoustic analysis was therefore presented. Then it worked out the acoustic radiated field in time domain with IFEM by SYSNOISE, the calculated results were com pared with the experimental results. The comparative result shows the validity of the proposed method.