For providing a better shelter condition, it is necessary to build a breakwater in Zhongzui Bay. In order to know whether mooring area meets the requirement after engineering construction and compare the mooring area between solid breakwater and permeable breakwater, a numerical simulation method is used in the sheltering harbor of Zhongzui Bay. The used Mild-slope equation which describes wave refraction, diffraction and reflection, considers the steep slope bottom and effect of energy dissipation. It has been validated to fit for simulating wave transformation in the coastal zone. Under extreme high water level and design high water level, wave fields in the calculation area of three wave types in three different return periods are simulated by using this method respectively. In addition, wave height in front of breakwater can be provided. Then the wave parameters and the mooring area of two occasions, with and without breakwater, are gained in calculation area. Based on these results, some conclusions are presented in the end.