Abstract: This study focuses on steel structure engineering and proposes a BIM-based carbon emission calculation method for the design and construction phases, along with the development of a corresponding computational tool. The research initiates with the construction of a refined BIM model compliant with modeling standards to ensure geometric accuracy, component integrity, and data traceability. By integrating material information extraction functionality, the system achieves automated acquisition and export of building material data, supporting Excel-based data interchange. Adopting a modular design approach, parameter configuration and calculation modules were developed to enable user-defined adjustment of key parameters such as emission factors and construction energy consumption. Results demonstrate that this method significantly improves the efficiency and accuracy of carbon emission calculations, providing a scientific foundation for green design and sustainable development in steel structure engineering. The key innovation lies in the deep integration of BIM technology with carbon emission quantification during design-construction phases, realizing full-process automation from model creation and data management to emission calculation. This approach offers reliable technical support for carbon reduction in the construction industry.