Sewage source heat pump is an efficient environmental protection and energy saving system. The particularity of wastewater quality makes the selection of heat exchanger equipment and the water quality corrosion and scaling of heat exchanger equipment become obstacles to the promotion of sewage heat recovery. According to the existing problems of the heat exchanger of the sewage source heat pump system and the characteristics of the plastic heat exchanger, a plastic heat exchanger is proposed to replace the metal heat exchanger. Through the plastic heat exchanger in corrosion, scaling, price and other aspects of metal heat exchangers and found that it has obvious advantages. The plastic heat exchanger resistance, strength, heat transfer performance analysis shows that the plastic heat exchanger in the sewage source heat pump is feasible. As an environmentally friendly and energy-saving heating and cooling system, heat pumps are more and more widely used. Native wastewater as a heat source / heat exchanger of heat pump system has some advantages unmatched by other types of heat sources / heat exchangers: 1) Can be obtained in large quantities. Large amount of primary sewage generated, the annual flow is almost fixed. 2) cool in winter and warm in summer. Winter sewage temperature is higher than the ambient temperature, the summer is generally lower than the ambient temperature. Such as Beijing Gaobeidian sewage treatment plant long-term measurement data show that the sewage water temperature is 13.5 ~ 16.5 ℃, higher than the temperature above 20 ℃; summer sewage water temperature is 22 ~ 25 ℃, lower than the temperature above 10 ℃. 3) contains a lot of heat. Due to the complicated water quality of the heat pump system, the long-term and stable operation of the heat exchange device will bring severe problems in the long-term operation of the heat pump system. test.