Conventional refrigerants HCFC and HFC have a negative environmental impact. Desiccants are chemicals with great affinity to moisture. Dehumidification is one of the most important processes in the liquid desiccant air conditioning system by solar energy. Liquid desiccant dehumidification was proved to be an effective method to extract the moisture from air with a relatively less energy. The dehumidification process is based on mass and heat transfer. This paper presents the experimental investigation on mass transfer during dehumidification process using two liquid desiccants CaCl2.2H2O and MgCl2. The tests are carried out in isothermal room with air flow. The aim of this study is to make a comparison in order to select the better desiccant. The results show that the mass transfer potential increases linearly with increasing the humidity ratio. The mass transfer rates increased with higher Reynolds number and the CaCl2.2H2O solution showed much better mass transfer than that MgCl2 in the dehumidification process. Then, the CaCl2.2H2O can be used in LDCS.