Abstract: There are many natural and artificial islands in our country, where the freshwater lens are precious freshwater resource and play an important role in supporting domestic water and the health of the groundwater -dependent ecosystems. Improving the groundwater storage of islands can effectively mitigate the widespread issues of water resources shortage of islands. This study presents some methods capable of improving oceanic fresh groundwater storage by using a low -permeability medium along the shore line. The effectiveness of the proposed method is validated through experimental and numerical studies. Field -scale numerical models are developed to analyze the possibility of the field application. The experimental fresh water -saltwater interface result is in good agreement with the numerical result, indicating that the proposed method has a great potential in preventing seawater intrusion and improving the freshwater storage. The numerical results show that for an imaginary island, the fresh groundwater storage can be increased by about 5 times after 8 years since the project is implemented. This study provides a new method for alleviating the issue of water resources shortage and realizing sustainable use of freshwater resources in island areas.