To　promote　China′s　Carbon　Peaking　and　Neutralization　Policy,　provide　data　support　for　energy　conservation　and　emission　reduction　of　metro　projects,　and　address　the　complex　and　cumbersome　problem　of　greenhouse　gas　quantification　process　in　the　construction　stage　of　metro　deep　foundation　pit　engineering,　a　modular　calculation　method　for　carbon　emissions　in　the　construction　stage　of　metro　foundation　pit　engineering　is　established　based　on　the　whole　life　cycle　theory.　Due　to　the　fact　that　the　metro　foundation　pits　are　temporary,　the　carbon　emission　calculation　process　is　divided　into　three　stages:　Upstream　material　production,　foundation　pit　site　construction,　and　material　transportation.　Furthermore,　the　greenhouse　gas　emissions　during　construction　process　of　the　02B　foundation　pit　and　the　pit　in　pit　of　the　Beijing　City　Sub-Central　station　comprehensive　transportation　hub　project　are　calculated　and　analyzed.　The　results　show　that:　(1)　The　CO2　emitted　during　the　construction　stage　of　02B　foundation　pit　and　the　pit　in　pit　reached　20　498.50　t　and　32　422.50　t,　respectively.　(2)　The　carbon　emission　in　the　construction　stage　of　the　metro　deep　foundation　pit　project　is　related　to　the　construction　method　and　support　strength　of　the　metro　deep　foundation　pit.　©　2022,　Editorial　Office　of　Tunnel　Construction.　All　rights　reserved.