The　macro-mechanical　performances　of　CFST　column　at　low　temperatures　can　be　significantly　affected　by　three　main　factors:　the　change　of　meso-material　properties,　the　filling　and　frost　heave　effects　caused　by　pore　ice,　and　the　interaction　between　each　meso-component.　Therefore,　a　three-dimensional　thermo-mechanical　sequential　coupling　mesoscopic　simulation　method　was　established　and　verified　by　existing　experimental　results　with　the　maximum　errors　within　10　%.　The　seismic　performances　of　CFST　columns　with　various　cross-section　sizes　(200-800　mm)　at　different　temperatures　(20,-30,-60　and-　90　degrees　C)　were　simulated　and　investigated,　with　focused　on　the　damage　mechanism　and　quantitative　analysis　of　the　low-temperature　effect　on　various　seismic　performance　indexes　(i.e.,　hysteretic　characteristic,　nominal　shear　strength,　ductility,　energy　dissipation　and　reparability)　as　well　as　the　corresponding　size　effects.　The　results　indicate　that　the　low　temperature　can　increase　the　nominal　strengths　(i.e.,　peak　strength,　yield　strength　and　ultimate　strength),　but　weaken　ductility,　energy　dissipation　capacity　and　reparability　of　CFST　columns.　With　the　increase　of　cross-section　size,　the　reparability　increases,　while　other　seismic　performance　indexes　decrease,　showing　the　size　effect,　which　tends　to　be　more　obvious　at　low　temperatures.　The　size　effect　on　peak　strength　at-90　degrees　C　is　enhanced　by　115.5　%　than　that　at　20　degrees　C,　while　127.9　%　for　yield　strength　and　113.5　%　for　ultimate　strength.　Based　on　research　results,　a　modified　size　effect　formula　for　calculating　shear　strengths　of　CFST　columns　considering　the　influence　of　low　temperature　and　structural　size　was　developed,　which　can　provide　references　for　seismic　design　of　large-sized　CFST　columns　in　extreme　low　temperature　environments.