Abstract: Rain gardens can effectively control the volumes and quality of rainwater runoff,but the application experience in islands is lacking.In the island area of Zhoushan,Zhejiang,the complete water balance method and indoor optimization experimental are used to design and construct a 50 m2 impervious rain garden. Through real-time monitoring runoff data of 4 precipitation events,this paper evaluates the operating effects of rain gardens in island areas under different rainfall intensities.The results show that the rain garden in the island area has good retention capacity,and no overflow during the monitoring period.The total runoff reduction rate is 64.60%～89.71%,with an average of76.64%.The flood peak reduction rate is 70.52%～91.23%,with an average of 84.76%,rainfall intensity is negatively correlated with the reduction rate of total runoff,and has little correlation with the reduction rate of flood peak.The rain garden has a good purification effect on SS,COD,NH₃-N,NO₃-N,TN,PO₄³⁺and TP in runoff,and the average removal rate is 82.26%,42.17%,66.70%,64.94%,58.64%,65.24%and 76.46%,respectively.The research can provides a reference for the design and application of rain gardens in island areas.