Polystyrene matrix was chloromethylated by chloromethyl ether or methylal and chlorosulfonic acid in order to investigate the effect of polymer matrix crosslinking on the polymeric reaction. Bead and macroporous type polystyrene matrix were used for chloromethylation. It was found that higher substitution ratio was obtained in macroporous type polystyrene matrix. Higher substitution ratio is owing to the fact that chloromethylating agent and solvent can be easily penetrated into macroporous type matrix resin. MMA-styrene copolymer matrix resulted in higher substitution when compared with polystyrene matrix. Due to interactions between polymer chains, considerable autocrosslinking was caused in macroporous type resin and low crosslinked resin matrix.