Carbon（C）sequestration　of　coastal　tidal　wetland　ecosystems　is　affected　by　metabolic　capacity　of　microbial　decomposers　to　maintain　nutrient　cycling　and　energy　flow.　To　explore　the　soil　microbial　metabolic　restriction　and　microbial　carbon　use　efficiency（CUE）of　different　plant　communities　in　coastal　tidal　wetlands，we　collected　the　soil　samples　from　the　surface（0~5　cm）soil　and　the　deep（20~40　cm）soil　in　four　wetland　habitats　in　the　Jiulong　River　estuary，which　are　the　mangrove　community，the　Spartina　alterniflora　community，the　community　dominated　by　the　mangrove，and　the　community　dominated　by　the　S.　alterniflora　in　the　ecotone　between　the　mangrove　forest　and　the　S.　alterniflora　marsh.　We　measured　the　soil　physicochemical　parameters，the　contents　of　soil　microbial　biomass　C，nitrogen（N），phosphorus（P）and　the　extracellular　enzyme　activities.　The　vector　length（VL）and　the　vector　Angle（VA）were　calculated　by　the　ratio　of　C，N　and　P　of　extracellular　enzyme　activity，and　the　microbial　CUE　was　calculated　by　the　biogeochemical　model.　Soil　microorganisms　in　the　four　wetland　habitats　were　generally　restricted　by　the　contents　of　C　and　P.　Microbial　CUE　in　the　surface　and　deep　soil　showed　different　rules　with　habitat　changes.　Microbial　CUE　in　the　surface　soil　significantly　changed　in　the　different　habitats，vegetation　competition　significantly　reduced　the　microbial　CUE，and　microbial　CUE　in　the　deep　soil　relatively　remained　stable　among　the　four　habitats.　RDA　analysis　showed　that　the　correlation　between　microbial　metabolic　limitation　and　environmental　factors　in　the　different　soil　layers　was　inconsistent.　In　the　surface　soil，soil　nutrients　were　positively　correlated　with　microbial　CUE，and　negatively　correlated　with　C　limitation；and　the　microbial　biomass　C，N，P　was　positively　correlated　with　CUE　and　P　limitation，and　was　negatively　correlated　with　C　limitation；while　in　the　deep　soil，microbial　CUE　and　C　limitation　were　not　strongly　correlated　with　the　SOC.　The　P　limitation　was　negatively　correlated　with　the　microbial　biomass　C.　Overall，our　findings　suggested，invasion　of　S.　alterniflora　into　mangrove　forest　significantly　affected　metabolic　characteristics　and　microbial　CUE　of　surface　soil.　Soil　microorganisms　in　the　mixed　plant　community　face　with　stronger　C　restriction，and　maintain　higher　C∶N　and　C∶P　of　extracellular　enzyme，and　lower　CUE，which　would　exacerbate　soil　C　pool　loss　in　coastal/estuarine　wetlands.　©　2023　Science　Press.　All　rights　reserved.