During the engineering structure materialization stage, greenhouse gas emissions predominantly arise from building materials and construction activities. This paper aims to quantify carbon emissions during the materialization of combined structures and propose a method to convert these emissions into economic costs for effective control. This study chooses combined structures materialization as the research object, the carbon emissions of the main materials and equipment in the building materialization process were calculated and studied based on BIM technology, and develops an automated carbon assessment system based on BIM. By utilizing the European Union Emissions Trading System, the economic conversion of carbon emissions offers a quantitative economic evaluation index for carbon emissions from the production, transportation, and construction activities of the combined structure. Finally, this study also incorporates recent carbon emissions trading prices to convert carbon emissions into economic costs, followed by a detailed economic analysis. The method proposed in this paper can effectively evaluate the carbon emissions during the materialization process of the combined structure, which is of reference significance for the selection of low-carbon materials in the design process, and provides case references for the research of low-carbon equipment.