Abstract: Through systematic studies of geology and hydrogeology of the Changshan Island with the data from hydrogeological drilling, pumping test and hydrogeochemical investigation, the regional geological and tectonic background, the hydrogeological conditions and the characteristics of groundwater environment for bedrock fissure water have been further recognized. The landform type of rolling South Changshan Island is complex. The exposed strata are mainly the Penglai group metamorphic rocks and Quaternary loose rocks and so on. Tectonic fractures, especially tensile fractures are widely developed on the island and the abundance of tectonic fracture water is high even the pore water in loose rocks is little. The hydrochemical types of bedrock groundwater at the South Changshan Island are mainly belonging to Cl-Ca, Na type, with a salinity ranging between 202mg/L-704 mg/L, Water quality is basically good. However, seawater intrusion and man-made pollution may bring negative impact to the quality of bedrock groundwater.