To design a floating production or drilling structure, we have to estimate the interacted responses among a floating offshore structure, risers and mooring lines in external forces. This study has focused a floating structure with riser. First of all, this paper has discussed with behavior of a forced oscillated riser model. First, model experiments in a water tank have been carried out in forced oscillation conditions to observe the behavior of a riser model. Second, the behavior of forced oscillated riser model has been estimated by two numerical mothods. These methods are based on Morison's equations, and CFD method, respectively, for calculating hydrodynamic forces around a 2D riser section. To validate corresponding of numerical estimation, experimental results have been compared with numerical results. From these results, the numerical methods have been confirmed as useful and appropriate.