Abstract: We have verified the formation of exciplex in the photopolymerization of acrylonitrile initiated with aniline.There are two routes involed,i.e.either through the excitation of the charge transfer complex of aniline and acrylonitrile or from the excited singlet state aniline and the ground state acrylonitrile to form excited complex which generates two kinds of radicals by proton transfer process,which both will be responsible for the initiation.