Abstract: The chloromethylation of crosslinked polystyrene (CPS) microspheres was performed using 1,4-bis(chloromethoxy)butane (BCMB) as the chloromethylation reagent. Then the nucleophilic substitution reaction between 5-amino salicylic acid and benzyl chloride groups on the CMCPS microspheres was conducted, and amino salicylic acid-crosslinked polystyrene resin (ASACPS) was obtained. The chemical structure of ASA-CPS resin was analyzed by the infrared spectroscopy. The effects of reaction conditions on the substitution reaction were examined, and the chelating property of ASA-CPS resin for metal ions was tested. The experimental results show that the prepared ASA-CPS resin possesses very high chelating ability for Fe(Ⅲ) ions, with adsorption capacity up to 3.77 mmol/g.