Recently many studies on the elastic response behavior of very large floating structures have been done. Such a very large structure is relatively flexible compared with other existing floating structures like large ships. For estimating the dynamic response behavior of structure, it is important to consider the deflection wave propagation based on fluid-structure interaction analysis. This paper deals with the dynamic response and strength of VLFS except peripheral part considering deflection wave propagation for the simple beam or plate model in regular waves. From analytical results considering fluid-structure interaction, effects of wave length and direction of incident waves on the response and strength are examined. Moreover, the dispersion relation of the deflection wave is also calculated.