The polymerization mechanism of various vinyl monomers in the presence of arematie tertiary amines has been studied．It was found that the mechanisms of differ-ent monomers are varied with the structure of monomer．Those monomers，such as Methacrylie esters．containing a一CH3 on the vinyl carbon atom could be polymerized with aromatic tertiary amine in the absence of light．while the monomers without a一CH3 group，such as methyl acrylate，aerylonitrile etc．would polymerize only under light．The mechanism of former case has been proposed that the a一CH3 gronp will be first oxidized by amine-O2 complex to the e orresponding hydroperoxide which then reacts with amine as redox system to produce the free radical species for initiation．Since in the later ease there is no such group to be oxidized，thus the mechanism has been proposed that the excited charge transfer complex (exeiplex) between mono-mer and amine will be formed under irradiation and then decompose to produce free radical species for initiation．The structural effect，both of the monomer and of the amine，on the rate of pho-topolymerization were studied．The activities of monomers and amines may be arranged in the following descending order as： It is revealed that both the electro．negative group on the double bond of monomer which acts as an accepter and the electro-positive group on the nitrogen atom of amine which aets as a donor would effectively in crease the rate of photopolymerization．