3D　flower-like　alpha-FeOOH　nanoparticles　were　synthesized　by　means　of　mild-temperature　reflux　method,　and　the　samples　were　characterized　via　X-ray　diffraction(XRD)　and　scanning　electron　microscopy　(SEM).　The　influencing　factors　such　as　the　reaction　time,　the　reaction　temperature,　the　concentration　of　urea,　and　the　amount　of　ethanol　were　systematically　investigated.　The　adsorption　capacity　of　the　alpha-FeOOH　nanoparticles　for　diclofenac　sodium　was　also　tested.　The　results　show　that　the　sample　prepared　with　0.　1　mol/L　urea　and　20%　(volume　fraction)　ethanol　at　90　degrees　C　for　6　h　is　in　high　structural　uniformity　with　good　crystal　quality　and　has　the　best　adsorption　capactity　of　199.　2　mg/g　for　diclofenac　sodium.　The　formation　mechanism　of　the　flower-like　alpha-FeOOH　nanostructures　is　involved　with　a　combination　of　oriented　attachment　and　epitaxial　overgrowth.　The　fresh　nanonuclei　are　formed　in　solution　at　the　early　reaction　stage　with　high　surface　energy,　then　aggregate　together　to　minimize　the　interfacial　energy.　The　olive-like　agglomerates　orient　into　short　clusters,　continue　to　grow　along　z　axis　till　the　complete　flower-like　structures　are　formed.