Mesoporous　modified　red　mud　adsorbent　(MRM)　was　prepared　via　acid　digestion　and　alkali　reprecipitation,　red　mud　(RM)　was　used　as　raw　material　in　our　experiment.　MgO　was　loaded　on　the　MRM　as　the　support　by　impregnation　method　in　order　to　increase　the　alkaline　active　site.　The　structural　properties　and　the　composition　of　samples　were　characterized　and　analyzed　by　BET,　XRF,　XRD,　CO2-TPD.　The　results　showed　that　the　specific　surface　area　of　the　MRM　was　about　28　times　higher　than　the　RM,　the　pore　structure　was　rich,　and　hematite　was　the　dominant　mineral　phase　composition　in　MRM.　It　could　be　seen　that　the　specific　surface　area　and　the　pore　volume　decreased　with　the　increase　of　the　Mg　loading,　which　was　due　to　the　occupation　and　the　blockage　of　the　pore　structure　of　the　MRM　support　by　MgO.　The　XRD　test　results　of　5%　MgO/MRM　did　not　show　the　peak　shape　of　MgO,　maybe　because　the　loading　was　small　or　Mg　dispersed　on　the　pore　channels　of　the　MRM.　When　the　adsorption　temperature　was　30,　the　CO2　adsorption　capacity　of　the　MRM　was　1.54mg/g,　the　adsorption　capacity　of　5%　MgO/MRM　was　2.26mg/g,　which　indicated　that　the　number　of　alkaline　active　sites　increased　significantly　after　MgO　loading,　and　the　chemical　adsorption　effect　enhanced.　With　the　increase　of　the　temperature,　the　adsorption　capacity　gradually　decreased.　The　results　of　the　CO2-TPD　test　showed　that　both　MRM　and　5%　MgO/MRM　were　dominated　by　chemisorption,　which　formed　the　carbonate　and　bicarbonate　structures.　©　2023　Chinese　Society　for　Environmental　Sciences.　All　rights　reserved.