In this paper, a novel heat pump system is proposed, which operates as a heat-source-tower heat pump with no frosting in winter, and as a hybrid refrigerant system consisting of a conventional chiller combined with a liquid desiccant dehumidification and evaporative cooling subsystem in summer. A validated mathematical model of the proposed system operating in summer is established to investigate the effects of key parameters, including solution to refrigerant flow ratio (FR), condensation heat recovery ratio (R-cond) and ambient parameters, on the cooling performance. Besides, this paper analyzes key factors that should be considered in designing the heat exchange area of the solution-cooled condenser (SCC). The results show that the maximum COP and ECOP of the heat pump system are 13.4% and 10.3% higher than those of conventional vapor compression refrigerant systems under the typical summer condition of Nanjing, respectively. The recommended range of FR is from 1.2 to 6 and that for R-cond is from 16% to 40%. Moreover, the proposed system is more superior to conventional ones when applied in hot and humid regions.