Abstract Liquid desiccant cooling system (LDCS) is an alternative air-conditioning system with good energy-saving potential. Dehumidification performance is the key part of LDCS; while desiccant variety and dehumidifier influence the dehumidification performance. However, few works have been done about how to select cost-effective liquid desiccant and good performance dehumidifier. To improve, we proposed a new method for selecting a cost-effective mixed desiccant group: it combines the non-random two-liquid equation (NRTL equation) with the desiccant cost to get the mathematical form of the cost-effectiveness. Meanwhile, through the comparison experiments among different dehumidifiers, we have found out some helpful tips for dehumidifier design: it achieves better effect with rougher surface and adsorption absorption complex plan. These progresses increase the dehumidification performance by more than 50% and could make LDCS more competitive in the future market.