In the present investigation, influence of gaps between multiple floating structures on wave forces is examined.Strong and complicate hydrodynamic interactions between the floating bodies are observed and the numerical computations have proved the existence of the sharp peak force response on each floating body at some special resonant wave numbers.The resonant wave number is also proved to be around kL=nπ(n=1, 2, ..., ∞) with a corresponding frequency shift.A small yet finite gap width will also give influence on the resonant frequency and resonant amplitude of the wave forces, but when the distance between two aligned box-shaped floating bodies becomes big enough, the hydrodynamic interaction can be neglected.The strong hydrodynamic interaction feature has its own important practical significance for the design of module structures and the links (connection) in the whole floating body system.Moreover, the importance is closely related to the hydro-elasticity analyses of a multiple box-shaped floating body system, in which local loads may be as important as the integrated loads.