In this paper, boundary integral equation method is used to study the hydrodynamic interaction effects between wave and two connected floating structures. The hydrodynamic interaction between the two bodies is considered. The amplitudes of the body motions are determined according to the motion equations of the two bodies and the continuous conditions at the connection between the bodies. In order to verify this method, the heave amplitude at the hinged joint and the relative angular deflection of two floating barges, which connected by a hinge, are calculated and compared with the results from Newman. The comparison shows that the present calculation agrees well with Newman's result except at the nearby of the resonant frequency of the system. At the resonant frequency of the hinged system the present result changes quickly, but Newman did not mention the phenomenon.