Linear type polystyrene was chloromethylated with chlormethylether under conditions of varied reaction temperatures, reaction times and ratios of chloromethylether to polystyrene. The amount of chloromethyl group introduced to the polystyrene increased and greater autocrosslinking was accompanied as the reaction temperature increased from 30$^{circ}C$ to 50$^{circ}C$. At the temperature as low as 30$^{circ}C$, more chloromethyl groups were introduced to the benzene unit in polystyrene, when greater proportion of chloromethylether was added to polystyrene. At the temperature above 50$^{circ}C$, however, the proportion of chloromethylether did not greatly affect the introduction of chloromethyl groups to benzene unit. Chloromethyl groups were introduced according to the first-order reaction rate.