A 3-D numerical wave tank (NWT) is proposed in this paper to calculate the wave propagation and hydrodynamics force based on the incompressible Navier-Stokes equations by using the commercial computation fluid dynamics (CFD) software. The volume of fluid method is used to capture free surface. CFD code to generate waves in the NWT is first validated by analytical theory to check its accuracy. Next, a cylinder structure model is introduced to study the interaction of the structure with the wave load. The experiment included a cylinder structure, which was set up in a flume, to compare the wave load against numerical results. The performance of the numerical model is validated and verified by several cases, and it shows very good agreement with the experimental test.