Chloromethylpolystyrene was synthesized as the precursors of chelate resin matrix available for recovery of uranium from seawater. The effect of various crosslinking agent, degree of crosslinking and external appearance of resin matrix on the chloromethylation have been investigated. High rate of chloromethylation was observed in ethylene geycol dimetlacrylate, butanediol dimethacrylate-crosslinked polystyrene compared to divinyl benzene-crosslinked polysyrene due to higher degree of swelling. In the chloromethylation reaction, maximum chlorine content was obtained between 1.5~2hour. After two hours, chlorine content decreased gradually due to autocrosslinking.