In　this　study,　coarse　sand-supported　zero　valent　iron　(ZVI)　composite　was　synthesized　by　adding　sodium　alginate　to　immobilize.　Composite　was　detected　by　scanning　electron　microscope　(SEM),　X-ray　diffraction　(XRD),　and　X-ray　fluorescence　(XRF).　SEM　results　showed　that　composite　had　core-shell　structure　and　a　wide　porous　distribution　pattern.　The　synthesized　composite　was　used　for　degradation　of　2,4-dichlorophenol　(2,4-DCP)　contamination　in　groundwater.　Experimental　results　demonstrated　that　degradation　mechanism　of　2,4-DCP　using　coarse　sand-supported　ZVI　included　adsorption,　desorption,　and　dechlorination.　2,4-DCP　adsorption　was　described　as　pseudo-second-order　kinetic　model.　It　was　concluded　that　dechlorination　was　the　key　reaction　pathway,　ZVI　and　hydrogen　are　prime　reductants　in　dechlorination　of　2,4-DCP　using　ZVI.