In recent years, with the development of Chinese construction industry and continuous pursuit of green and sustainable development goals, the designers have gradually adopted BIM technology to analyze building energy conservation. On the basis of summarizing the concept of green BIM idea and corresponding analysis software, this paper analyzes the green energy saving of multi-storey buildings through practical case study by using green building Siwell software. Firstly, the software is used to read the building drawings, and then to select appropriate building materials, as well as to simulate and optimize the design of the energy saving, daylighting and sunshine of the building according to the corresponding technical standards. By using the software, it can be intuitively shown the impact of basic building data, energy loss and natural conditions on the building. The research results of this paper can provide design basis and reference standards for similar schemes in this region, and fully demonstrate the advantages and broad prospects of BIM technology.