The photo-induced polymerization of acrylonitrile in concentrated aqueous zinc chloride solution was carried out. It was found that the rate of polymerization of acrylonitrile is remarkably enhanced and crosslinked polymer was resillted in concentrated aqueous zinc cllloride solution. The rate of polymerization is retarded in the presence of oxygen showing the nature of radical polymerization, however, the degree of dependence on oxygen is not so significant because the diffusion of oxygen is depressed in highly viscous reaction medium. The enhancement effect of zinc chloride on the polymerization was explained in terms of complex formation of divalent zinc cation with acrylonitrile. It was impossible to remove zinc chloride from the crosslinked polymer after polymerization. The colorless transparent polymer. containing zinc chloride and water shows a high electrical conductivity, having the order of magnitude of 10-2 Scm-1 and is red colored by heating to 15$0^{circ}C$. It has been cleared that the red color appearance is closely related to the disappearance of the absoption band at 2270cm 1 due to the pendant nitrile group on the IR spectrum of the crosslinked polymer containing zinc chloride and water, which implies that pendant nitrile group. completed with divalent zinc cation, is preferentially converted to a chromophore unit having the structure of conjugated keten-imine at lower temperature than free nitrile is.