Currently, buildings in the U.S. account for more than 40% of total primary energy. In China the same figure is 20%. Detailed building energy analysis and benchmarking based on energy monitoring is becoming vitally important for the evaluation of energy efficiency technologies and related policy making. This paper focuses on methods and challenges in energy benchmarking of office buildings between the U.S. and China, based on the experiences and outcomes of a joint research project under the U.S.-China Clean Energy Research Center for Building Energy Efficiency. First, benchmarking methods were presented, including data analysis methods, required data, building selection criteria and a standard data model for building energy use. Annual electricity use benchmarking was performed from a sample of selected office buildings in both countries, with the aim of identifying and understanding the main discrepancies and key driving factors. Benchmarking challenges were then summarized and discussed, and some potential solutions were proposed, including the process of building selection, data collection and clean-up, and specific analysis techniques. Recommendations were proposed for future work to improve the process and outcomes of building energy benchmarking between the two countries.