Abstract: The article introduces the reaction mechanism of arene electrophile substitution, and describes the synthesis of halogenated polystyrene(PS) by modifying macromolecules. According to the difference of active order of aryl ring substituted by chlorine,bromine and iodine, chloromethyl ethyl ether, bromine and iodine are respectively used in the PS substitution under the different catalytic conditions.The degree of substitution of polymer doped by bromine or iodine can be controlled by reaction time, while that of chloromethylation PS controlled by the stoichiometry.