Based on a open-source numerical software of wave, COBRAS, a two-dimensional numerical model is developed to study the wave propagation and evolution characteristics over a beach in Benin, in which the free surface is captured by the Volume-of-Fluid method and the Reynold stress is obtained by solving the k-epsilon equations. The numerical model is validated with the experimental data for the free surface of a solitary wave during the shoaling and breaking over a slope. The proposed model is then used to study the shoaling and breaking processes under ordinary and extreme wave conditions. The results show that the waves break near the sandbar under the ordinary wave condition. However, under the extreme wave condition, they start to break 200 m away from the sandbar, and during the interaction of the rundown water and the incident wave, vortexes shall be formed over the sandbar. In the breaking zone, the water velocity is relatively large, which can be 7.5 m/s under the ordinary wave condition and even reach 12.4 m/s under the extreme wave condition. With the increase of the nonlinearity of the incident wave, the runup height increases, and overtopping occurs under the extreme wave condition.