In order to save energy, the author developed a type of air-wastewater source heat pump (AWSHP) water heater system. What presented here is about the experimental performance and empirical models of the AWSHP system. Experiments and analysis showed that when the temperatures of waste water and city water varied in the ranges of 16.9~35.1 °C and 18.3~32.6 °C, respectively, the AWSHP system could produce 41.2~53.9 °C hot water with flow rate of 3.53×10-5~9.31×10-5 m3/s. The coefficient of heating performance (COPh) varied from 3.89 to 5.35. On the basis of energy balance, synthetic degree of grey incidence (SDGI) and grey-box methods, it was found that the COPh and hot water flow rate depended on the ratio of inlet and outlet temperature differences of waste water and hot water, i.e. ΔTw/ΔTh. The input power of compressor was proportional to the outlet temperature of hot water. Thus, the empirical correlation equations were obtained.