BEU accounting and assessment is a fundamental task for development of energy efficiency in buildings. The traditional methodology is based on caloric value of energy carriers, which is only relates to energy quantity. To address a comprehensive assessment, an exergy assessment methodology is put forward in this paper. Furthermore, in existing China's statistical yearbook, there is no specific item for building energy use. This paper processes analysis for statistical yearbook and acquires relevant rough data of building energy use. With the methodology, an analysis of BEU in Hot Summer and Cold Winter Zone of China is employed in the paper. According to analysis, the BEU (only refer to use in building operation in this paper) accounts for about 20% in local energy use. And the exergy efficiency is only around 0.3 in building energy supply, which is quite different with that by traditional methodology. From Burden Index of BEU, it can be found that BEU takes large share in local exergy production and more developed takes more. Especially in Shanghai, the Burden Index of BEU is at 7.0, which is very over-burdened. The building sector consumes the resources reserved in last thousands of years.