Air conditioning system based on liquid desiccant has been recognized as an efficient independent air humidity control HVAC system. To improve thermal coefficient of performance, a novel two-stage liquid desiccant dehumidification system assisted by calcium chloride (CaCl2) solution is developed through exergy analysis based on the second thermodynamic law. Compared with the basic liquid desiccant dehumidification system, the proposed system is improved by two ways, i.e. increasing the concentration variance and the pre-dehumidification of CaCl2. The exergy loss in the desiccant-desiccant heat recovery process can be significantly reduced by increasing desiccant concentration variance between strong desiccant solution after regeneration and weak desiccant solution after dehumidification. Meanwhile, the pre-dehumidification of CaCl2 solution can reduce the irreversibility in the regeneration/dehumidification process. Compared to the basic system, the thermal coefficient performance and exergy efficiency of the proposed system are increased from 0.24 to 0.73 and from 6.8% to 23.0%, respectively, under the given conditions. Useful energy storage capacity Of CaCl2 solution and LiCl solution at concentration of 40% reach 237.8 and 395.1 MJ/m(3). respectively. The effects of desiccant regeneration temperature, air mass flux, desiccant mass flux, etc., on the performance of the proposed system are also analyzed. (C) 2009 Elsevier Ltd. All rights reserved.