In this paper, according to the fact that the interior load is not considerable, the area of interior zone is small, and the superfluous heat is little in most of the buildings, which restrict water loop heat pump to be widely used, the authors put forward a method utilizing low level heat source to solve the problem, then give several types of low level heat sources, introduce their characteristics , present the principle diagram of water loop heat pump air conditioning using these low level heat sources. Compared with conventional systems, these systems have not only nicer efficiency of energy saving, but also the significance of environment protection, which broadens the application range of water loop heat pump air conditioning system.