The　SBA-15-supported　polyethyleneimine　(PEI)-modified　layered　double　hydroxides　(xLDH-yPEI/SBA-15)　were　prepared　by　the　in　situ　coprecipitation　method,　and　their　CO2　adsorption　performance　and　involved　mechanisms　were　studied.　After　loading　of　PEI　and　LDH　on　the　surface　of　SBA-15,　the　composite　materials　still　maintained　an　ordered　two-dimensional　hexagonal　porous　structure.　The　optimal　CO2　adsorption　capacity　(2.01　mmol/g)　of　40LDH-2PEI/SBA-15　at　50　C　was　1.88　times　larger　than　that　(1.07　mmol/g)　of　SBA-15.　Such　an　excellent　CO2　adsorption　capacity　of　40LDH-2PEI/SBA-15　was　associated　with　its　high　BET　surface　area,　abundant　basic　sites,　and　fast　adsorption　kinetics.　The　regeneration　efficiency　of　40LDH-2PEI/SBA-15　was　still　94%　after　11　recycles.　We　are　sure　that　the　SBA-15-supported　PEI-modified　LDH　materials　are　good　performance　adsorbents　for　the　adsorption　of　carbon　dioxide.