Radiation-induced polymerization of acrylonitrile in frozen agueous solutions of various metal halides at -78$^{circ}C$ was discussed. The bromide or chloride of zinc (II) were found to the most effective in accelerating both the rate and degree of polymerization. The enhancement effect of various metal cations and anions was discussed on the basis of the stability of metal-monomer complex. No particular difference in IR spectrum between the polymer obtaind from this experiment and conventional polyacrylonitrile polymerized by radical initiator was observed, however, the appearance of 1670cm-1 absorption band, which might be attributed to the presence of ketene imine structure, implies the possibility of the polymerization at the triple bond of pendant nitrile group at the monomer under such condition.