Abstract: Air-cooling units are mainly adopted for heating in the north of China. Characteristics of air-cooling units and the basic ways of circulating water heating network are introduced. According to the different characteristics of the current mainstream direct air-cooling units of and basic heating modes,the schemes of conventional heating, heat pump heating, high back pressure heating are put forward. After comparative analysis of the three heating schemes,the critical curve applicable for each scheme is formed,which has a certain guiding significance for the selection of heating reform scheme for the same type of units.