The solar-air compound heat pump system which core component is a three medium composite heat exchanger is a new heat pump system. Compared with the conventional air source heat pump system, the COP of the new dual heat source heat pump system is at least increased by 40%, and the energy-saving effect is obvious. At present, the only dual heat source composite heat exchanger used in heat system is a finned-tube three medium composite heat exchanger. With the heat exchanger, the synchronous heat exchange between a liquid heat source, a gaseous heat source and a refrigerant could be realized, and the performance of the heat pump system could be effectively improved. But the structural defects of the finned-tube three medium composite heat exchanger result in processing difficulty, and it is difficult to form a batch production with the present processing technology. The hidden sealing danger of the heat exchanger also exists. In the paper, a new three medium composite heat exchanger has been designed. The structural flaw of the finned-tube three medium composite heat exchanger has been better avoided. And it makes the process easier and the batch production more convenient.