随着城市地下交通系统的不断发展，地铁车站基础设施建设项目日益增加，其环境成本亦显著增长。以中国地铁车站基础设施建设中基坑工程的碳排放为对象，开展基础设施碳排放高效在线计算方法及减排方案研究。提出基于基元法的碳排放高效在线计算方法，利用基坑分项工程特点，高效评估碳排放环境影响并形成有效的碳减排工程优化策略方案。同时，基于所提出计算方法，研发面向地铁基坑工程基元的web轻量化Metro Foundation Pit Carbon Emission Calculation System (pit-MCCS)碳排放计算系统，以提高碳排放计算效率及结果可视化水平，并支持动态更新和多方协同。pit-MCCS计算系统已成功应用于上海某地铁车站基坑工程案例，快捷精准地计算出该基坑工程总碳排放量为102 218.08 t。分析发现，地下连续墙的混凝土浇筑是主要的碳排放源，尤其是钢筋和混凝土材料的使用。此外，运输和施工阶段也显著贡献了碳排放。为应对地铁基坑工程高碳排放问题，研究提出了优化材料选择、更新施工机械、以及现场施工方案优化等可行的工程优化策略方案。

With the continuous development of urban underground transportation systems, metro station infrastructure construction projects have increased significantly, along with their environmental costs. This paper addresses the carbon emission issues in China's metro station foundation pit infrastructure engineering by proposing an online efficient carbon emission quantification approach based on the element method. This method efficiently assesses environmental impacts and develops effective carbon reduction strategies by leveraging sub-project characteristics. Additionally, the paper introduces a lightweight, metro foundation pit element-oriented web tool, the Metro Foundation Pit Carbon Emission Calculation System (pit-MCCS), which enhances carbon emission estimation efficiency and visualization, and supports dynamic updates and multi-party collaboration. The pit-MCCS system was successfully applied to a metro station foundation pit project in Shanghai, accurately calculating total carbon emissions at 102 218.08 t. Analysis reveals that the main sources of emissions are concrete pouring of diaphragm walls, particularly the use of steel and concrete, with significant contributions from transportation and construction phases. To address high emissions, the study proposes feasible strategies, including optimizing material selection, updating machinery, and refining construction plans.