This article introduces the application of building energy efficiency software in foreign countries, studies the development background, overview and technical route of the "Energy Star" project launched by the U.S. Environmental Protection Agency, and analyses the building energy efficiency comparison work carried out in China. This article suggests that China should enlarge the data base of building energy efficiency through multiple channels when developing building energy efficiency comparison tools, find basic data that are suitable for building energy efficiency comparison in China, and develop internet-based building energy efficiency comparison tools.