Absorption heat pump (AHP) is considered to be the most competitive equipment for energy saving when it uses high grade heat source to recover waste heat [1]. In recent years, the thermodynamics of real AHP cycle has been performed and many significant results have been obtained [2]. Some researchers analyzed the performance of the three-heat-reservoir heat pump cycle with the loss of heat resistance [3,4], with the loss of heat resistance and internal irreversibility [5], and with the loss of heat resistance, heat leakage and internal irreversibility [6]. Kodal et al. [7] analyzed the thermo economic performance of the three-heat-reservoir heat pump cycle. Chen et al. [8] optimized the relationship of the performance and the heating load of a three-heat-reservoir heat pump. A three-heat-reservoir absorption heat pump cycle is a simplified model of an absorption heat pump in that the temperature of the absorber is equal to that of the condenser, but in a real absorption heat pump usually it is not. The working fluid usually works in four different temperature levels in a real absorption heat pump cycle. Thus, some researchers established four-heat-reservoir absorption heat pump cycle with the loss of heat resistance and internal irreversibility [9], and with the loss of heat resistance, heat leakage and internal irreversibility [10,11]. In the studies of the internal irreversibility, almost just one internal irreversibility parameter is introduced, which could not distinguish the generator–absorber assembly and evaporator–condenser assembly. And when studying the correlation of system performance, a parameter was always