In order to identify the carbon emission characteristics during the construction period of highways in Yunnan Province, a life cycle assessment (LCA) framework based on the ISO 14040/14044 standard is constructed, which systematically covers the whole process of material manufacturing, transportation and construction, and integrates BIM modeling, path optimization, and machine learning prediction mechanism to carry out the component-level carbon intensity actuarial and multi-scenario comparative analysis, taking the Kunchu Highway Reconstruction and Expansion Project as an example. Analysis. The study found that the carbon emissions in the material manufacturing stage accounted for 73.4%, of which cement and asphalt were the main sources of emissions; by replacing high-carbon materials and optimizing the transportation path, the total emission reduction potential of 20.8% could be achieved. The BIM-LCA-ML integrated platform constructed has good assessment accuracy and intervention value, and verifies the application prospect of intelligent pathways in green infrastructure construction.