Abstract: We verified the formation of exciplex in the photopolymeriza-tion of acrylonitrile initiated with aniline.There are two routes to form exciplex,i.e.either through the excitation of the charge transfer complex of aniline with acrylonitrile or from the interaction of the excited singlet state aniline and the ground state acrylonitrile.Then it is followed by proton transfer proqess,leading to the generation of two kinds of radicals,which are responsible for the initiation.