Magnetic　porous　Fe3O4/MRCS　polymer　composite　was　prepared　by　reacting　melamine-formaldehyde　resin　with　chitosan　in　the　present　of　amino　modified　Fe3O4　nanoparticles　and　used　as　adsorbent　for　acid　red　18　azo　dye　removal.　The　Fe3O4/MRCS　was　characterized　by　TEM,　SEM,　XRD,　TGA　and　BET　analysis.　The　Fe3O4/MRCS　possessed　high　BET　surface　area　(226.6　m2/g),　characteristic　pore　properties　and　facile　magnetic　separation　function.　The　average　pore　width　is　6.5　nm　and　the　pore　volume　was　0.68　cm3/g.　The　Fe3O4/MRCS　presented　enhanced　high　adsorption　performance　toward　acid　red　18.　It　removed　99.　65%　of　acid　red　18　(100　mg/L)　when　the　adsorbent　amount　was　over　0.8　g/L.　It　was　found　the　absorption　was　depended　on　pH　and　the　removal　efficiency　decreased　with　pH　increased.　The　maximum　adsorption　capacity　of　acid　red　18　reached　as　high　as　301.0　mg/g.　The　adsorption　kinetic　followed　the　pseudo-second-order　kinetics　model　and　the　activation　energy　of　the　adsorption　process　was　38.40　kJ/mol.　The　adsorption　isotherms　were　best　fitted　to　the　Redlich–Peterson　isotherm　equation.　Thermodynamic　studies　indicated　the　adsorption　process　was　spontaneous　and　endothermic　in　nature.　The　adsorption　mechanism　study　showed　the　adsorption　was　a　heterogeneous　chemisorption　process　with　multiple　interactions,　involving　pore　filling,　electrostatic　attraction,　affinity　interaction,　intra-particle　diffusion,　π-π　interaction　and　polymer　chain　inclusion　and　polymer　net　trapping.　In　comparison　with　other　reported　adsorbents,　the　magnetic　porous　Fe3O4/MRCS　showed　superior　adsorption　performance　for　acid　red　18　removal.　©　2019　Elsevier　B.V.