Autocrosslinking reaction accompanied in polymeric reactions was investigated quantitatively. The degree of autocrosslinking was measured in chloromethylation of EGD crossliilked polystyreile. The finding from this study is that, in case of crosslinked polystyrene, the rate of autocrosslinking reaction of gel-type polystyrene is faster than that of macroporous-type. And the autocrosslinking reaction is terminaled in an hour from the initial reaction. In induced autocrosslinking of chloromethylpolystyrene obtained from polymerization of chloromethylstyrene monomer, initial autocrosslinking stage governs the whole crosslinking reaction so predominantly that the DVB and EGD crosslinking do not marc much difference. It is proved that the accompanying crosslinking reaction, introduced by the autocrosslinking. has a more significant elect on the polymeric reaction than the crosslinking agent used in chloromethylpolystyrene polymerization.