Permeability is the capacity of a soil for transmitting a fluid, e.g., a salt solution, through soil pores. The permeability coefficient K is an important measurement of the soil permeability, which is affected by various factors. The existing research on the permeability of sandy soil is basically carried out in the freshwater environment. However, the calcareous sand is a typical marine sedimentary sand, which is deposited in the seawater environment with certain salt concentrations. In order to investigate the influence of void ratio, particle size and concentration of the salt solution on the permeability of calcareous sand in a salt solution environment, constant head and falling head permeability tests were carried out using the meter KAST-soil saturated hydraulic conductivity. The microscopic characteristics were investigated through Zeta potential and contact angle tests. The results showed that the mean particle size has the greatest influence on the permeability coefficient of a calcareous sand, and the change of the mean particle size will even lead to the difference in the order of magnitude of the permeability coefficient. The permeability coefficient (K) is negatively correlated with the salinity of the transmitting solution (P), and positively correlated with the porosity (n) and the mean particle size (da). A model for predicting the permeability coefficient of calcareous sand taking into account the salt content of transmitting solution has been proposed based on the current experimental studies on the influencing factors. The proposed model can provide a tool for assessing the permeability of artificially reclaimed islands and reefs in the South China Sea and analyzing the evolution of ground freshwater.