An experimental method was refered to measure the behaviour of coadsorption equi-librium properties in a zeolite-wet air system. With the use of the present method, theequilibrium properties of water vapor adsorption on synthetic zeolite 13X and natural zeolitewere determined at various temperatures from 15℃ to 300℃ and water vapor pressures inthe range 1423.1Pa-5758.9Pa. Based on adsorption theories, the Langmuir model was usedfor correlating the equilibrium data of the isothermic coadsorption for the two zeolites. Thecoadsorption equilibrium equations of the two zeolites were also developed. The LgP-1/Tequilibrium diagrams for the zeolites were computed using the Langmuir model. The resultsshow the calculated values fit fairly goog to well the experimental ones.