Increase of human population has recently led to increase of wastes. Currently, disposal of wastes in landfills is taken to accounte as a common stertagy of waste management in many countries. One of the major concerns involved in landfills is seapage of rain water and leachate into underground water.one of these solutions is using Geosynthetics clay liner (GCL) insolate landfills. GCL, is mainly a member of Geosynthetic's family which is considered a barrier and restrictive of leachate immigration. GCL, is usually consisting of two non-woven layers of Geotextile on both sides and a core layer of sodium bentonite. In fact, GCL is a competitor product regards to eomembrane wich has been recently introduced to the market. On the other hands Isfahan is an industrial city. Consequently, a large amount of waste is produced daily. It is clear that always some waste shoud be buried in landfills including hospital waste. Fortunately, the hydraulic conductivity of GCL is low which provides GCL as a superior structure to protect the health of groundwater resources in The environment.the main aim of this study is investigating of hydraulic behavior of GCLs. it is clear that several parameters determine the permeability of GCL therefore, the independent variables of this study included type and areal density of clay, type and areal density of Geotextile, water pressure on GCL and the hydration effect. Consequently, 23 samples of GCL were prepared in accordance with the experimental designe. permeability and self- healing ability of samples were measured experimentally and evaluated statistically by using anova method. It was also revealed that the hydration process on GCL can demonestrately decrease the hydroulc conductivity of samples. GCL s with more value of areal density and thickness present lower hydraulic conductivity rather than other smples. Investigation of self- healing characteristics of samples illustrates that higher content of sodium in bentonite gives superior performance in slf- healing property. In the final, it was tyied to model the concept of self- healing phenoment of GCL by using Yong- laplace theory. Keyword: Geosynthetic clay liner, permeability of GCL, landfills, hydraulic conductivity GCLs