The main focus of this paper is to develop a new methodology for simply determining water retention curves (WRCs) of geosynthetic clay liner (GCLs) under high suction values. To this end, tests were conducted using vapor equilibrium method using over saturated salt solutions. This controlled suction technique is broadly in line with the suction gap required to establish the WRC of GCLs at first stage of hydration. This method consists in placing GCLs specimens in a controlled relative humidity chamber until equilibrium is reached. Specimens will thus adopt the suction provided by the salt solution used. Consequently, this vapor controlled system will ensure a homogeneous suction distribution into the specimen. It prevents the capillary break provided by the geotextile between the suction measure-ment/control system and the bentonite as part of the GCL specimen as has been seen in the literature while using a liquid controlled suction system. Experiments were conducted on two GCLs: a needle punched GCL containing sodium bentonite and a stitch-bonded GCL containing powdered calcium ben-tonite. Test results will be compared to each other and to results from previous water retention studies car-ried out on GCLs in order to check the suitability of this method.