A very large floating oil storage vessel which is the main structure of ocean oil reserve is the Very Large Floating Structure (VLFS), thus hydroelastic response of the oil storage vessel is an important part of research work. By using of sine mode shape function, first the radiation potential and hydroelastic response was expressed in terms of the modal superposition method. Then the velocity potential and fluid stress was solved on body surface of a quarter model according to the structure symmetry by means of the Green function method based on 3D potential theory. Finally, hydroelastic response of the oil storage vessel, deflection of the vessel bottom and bending moment were calculated by use of the hydroelastic equation of motion. Hydrodynamic parameters also analyzed with the water depth and wavelength, which provide a method to future design and work.