Overtopping wave energy converter is an offshore wave energy converter for collecting the overtopping waves converting the water pressure head into electric power through the hydro turbines. This paper presents a numerical wave tank based on the commercial CFD code Fluent. The Reynolds averaged Naiver-Stokes and VOF model is utilized to generate the 2D numerical linear propagating waves, which has been validated by the analytical solutions. Several incident wave conditions and shape parameters are calculated in the optimal designing investigation of the overtopping characteristics and discharge for the overtopping wave energy converter.