In order to apply as a desiccant for desiccant cooling system, zeolites were modified. As a result of comparison of adsorption isotherm, the zeolites treated by EDTA 0.5∼0.6g/g zeolite and HCl 0.3M had the optimal adsorption isotherm.(separation factor (R)=0.1). The amount of adsorbed water on HCl treated zeolite decreased as the HCl concentration increased, but in case of EDTA treated zeolite, the deviation was small so EDTA treated was more efficient.