The study and design of energy conservation has gradually become a hot and key issue in architecture. One of the core contents of such concepts as green architecture, ecological architecture, sustainable architecture, organic architecture is how to reduce high energy consumption of buildings. The study of building energy conservation has been carried out in subjects of architectural thermal engineering and energy conservation for almost 30 years. The central and local governments have set up special management agencies and departments of building energy conservation; building research institutes at all levels and numerous universities have set up research institutions for study of building energy conservation and issued a series of policies and regulations and technical standards, which received an enthusiastic response from industrial circles and have produced tens of billions of production. However, more than 95% of the existing buildings and more than 80% of new buildings of China belong to those with high energy consumption. The paper tries to interpret the deep reason of the phenomenon from the aspects of society, technology, etc. for discussion of researchers in the field of architectural thermal engineering and energy conservation.