In this paper, a hybrid element method(HEM) for the evaluation of the hydrodynamic responses of arbitrary-shaped offshore structures is studied. The hydrodynamic pressure forces are assumed to be inertially dominated, and viscous effects are neglected. The mathematical formulation procedure of the hybrid element method with the analytical eigenseries solution is established systematically. The computer program based on the HEM has been developed, and applied to solving the wave diffraction and radiation problems for arbitrary shaped structures. From comparisons of the results obtained by using the other avaliable solution methods, the method for the evaluation of the hydrodynamic forces using the HEM and the computer program developed here have been proved to be valid.