Calcareous clay is a kind of hydraulic reclamation coral foundation soil, whose permeability is of great significance for the construction of coral reef island projects. Based on the GDSPERM automatic environmental geotechnical permeability test system, a series of consolidation and permeability joint tests of calcareous clay of an reef island in the South China Sea were carried out, and the effects of void ratio, consolidation history, consolidation pressure, hydraulic gradient and pore fluid ion concentration on the permeability characteristics of calcareous clay were studied. The fitting analysis of the nonlinear relationship between the void ratio and the permeability coefficient of the calcareous clay was carried out, and a series of permeability laws of the calcareous clay have been summarized. The results show that the permeability coefficient of calcareous clay is about 10^-6 cm/s, and it does not change with the change of hydraulic gradient. There is an initial hydraulic gradient in its permeation; The consolidation history has a great influence on the permeability of calcareous clay. Under the same void ratio, unconsolidated soil samples show lower permeability; The permeability coefficient of calcareous clay decreases with the increase of consolidation pressure, and the decrease does not exceed an order of magnitude; As the void ratio increases, the permeability coefficient of the calcareous clay increases accordingly, and the relationship between the two is nonlinear. The "lg[k_v(1+e)]-lg e" model has a better fitting effect, which is considered to be the optimal nonlinear permeability model for calcareous clay; The permeability coefficient of calcareous clay decreases with the increase of NaCl concentration of pore solution.