In order to change the status quo of lacking holistic and intuitive research on building energy efficiency in China, an online virtual energy-saving and environment-friendly building system based on VRML was proposed. The two subsystems of virtual simulation technology, “virtual reality” and “energy consumption simulation,” were integrated and applied to the design research of building energy efficiency. On the basis of inheriting the advantages of the traditional way, the independent application mode of the two was changed. The application analysis was carried out using a real energy-saving demonstration project as the research object. The experimental results showed that the energy-saving rate of the enclosure structure of the three buildings was 35.742%, 30.408%, and 35.696%, respectively. It was concluded that the system provided a more systematic and intuitive method to the design and research of building energy efficiency.