In this study, calcareous coral sand samples from four stations on an island in the South China Sea were measured by common methods. Based on test parameters, numerical simulations of freshwater storage capacity were conducted by FEMWATER. The result indicates that the surface of the dredged calcareous coral sand in the South China Sea is mainly composed of medium and fine grains, and the porosity is mostly between 0. 35 and 0. 51. Meanwhile, the permeability coefficient and specific yield vary widely in different place, from 0. 023-12. 73 m/d and 0. 01-0. 10, respectively. There is a close relationship between the thickness and resource storage of fresh water lens and the hydrological parameters of calcareous coral sand. Among these parameters, the specific yield has the greatest influence on the resource storage of freshwater lens on the coral islands. Compared with the natural calcareous coral sand of Xisha Islands, the calcareous coral sand of this study is finer in size and particles are mostly flaky with poor roundness, which reflects the differences in hydrodynamic conditions and reef-building organisms.