Abstract: Data exchange between BIM (Building Information Modeling)-based application software and energy simulation tools such as EnergyPlus is a critical problem for developing BIM-based building energy-efficient design software. Although there are several related studies, neither the specific mechanisms nor commercial software have been published. In this paper, through analyzing the IFC (Industry Foundation Classes) standard which is the mainstream standard of BIM data, and the IDF (Input Data File) format which is the input format of a well-accepted software for the analysis, i. e. EnergyPlus, both the IFC-based model of design data and the IDF-based information model for the analysis of building s energy consumption were established. Then the mechanism for transformation from the former to the latter was formulated. Finally the mechanism was implemented by establishing several key algorithms in the application software and verified for a project of building design. It is shown that the established mechanism can improve the efficiency of preparing the model for the analysis significantly. This research lays a solid foundation for the development of BIM-based building energy-efficient design software.