Zhoushan City in Zhejiang Province is the focus of China’s reclamation area, and it also has a great influence on the groundwater quality. Based on the observed data of groundwater level and chloride ion concentration, groundwater quality in the next 6 years in Zhoushan area is predicted and analyzed by using groundwater numerical simulation software GMS. According to the comparison of observed groundwater level and simulated groundwater level at the end time, it is found that the whole water level in the filling area has the small fluctuation, which is within the range of 1 m. And the highest concentration of chloride ion is in the eastern coastal area. The prediction results indicate that there is no obvious trend of sea water with high chloride ion concentration to land. Under the condition of the current groundwater utilization, the groundwater level in Donggang sea area of Zhoushan is stable, and the chloride ion concentration has a slight decrease trend.