The　coupling　of　climate　warming　and　microplastics　may　affect　the　dynamics　of　arsenic　bioavailability　in　estuarine　sediments,　but　the　specific　processes　and　regulatory　mechanisms　of　this　phenomenon　remain　poorly　investigated.　In　this　study,　a　typical　subtropical　estuary　-　Min　River　estuary　was　selected　to　explore　the　dynamics　pattern,　composition　characteristics　and　regulatory　mechanism　of　arsenic　bioavailability　in　sediments　under　the　coupled　influence　of　climate　warming　and　microplastics　(type　and　dose)　through　incubation　experiments　by　utilizing　DGT　techniques.　The　results　showed　that　the　high-dose　PLA-MPs　significantly　enhanced　the　arsenic　bioavailability　after　warming,　while　low-dose　PET-MPs　inhibited　the　effect.　High-dose　PET-MPs　and　low-dose　PLA-MPs　significantly　promoted　the　oxidation　of　arsenic　(III)　after　warming,　while　low-dose　PET-MPs　and　high-dose　PLA-MPs　inhibited　the　effect.　The　interaction　of　temperature,　type　and　dose　of　MPs　significantly　affected　arsenic　bioavailability.　The　abundances　of　Bacteroidota　decreased,　while　the　abundances　of　Chloroflexi　and　Desulfobacterota　increased　significantly　after　warming.　The　correlation　between　microorganisms　and　the　bio-As　was　decreased　by　warming.　These　findings　provide　valuable　insight　for　understanding　the　complex　interplay　of　climate　warming　and　MPs　on　As-contaminated　estuary.　©　2025　Elsevier　B.V.