Saltwater intrusion has become a major hazard in the context of global change,which greatly affects coastal development. By field water sampling and high-resolution resistivity measurement,we attempted to detect the mechanism of seawater intrusion in the Northern Changshan Island. According to the results and compared with previous studies in the Northern Changshan Island,we assess seawater intrusion in this area and claim the potential of our study for seawater intrusion and groundwater management.