A polymerizable photoredox system consisting of 4-methacryl oxybenzophenone (MABP) and N,N-dimethylaminoethyl methacrylate (DMAEMA) used for the photopolymerization of acrylonitrile (AN) was studied. It was found that the polymerization rate is proportional to the 0.93th power for the AN concentration, the 0.28th power for the MABP concentration, and the 0.25th power for the DMAEMA concentration. The overall activation energy of the polymerization obtained is 30.43 kJ/mol. The recorded ESR spectrum indicates that the excited-state MABP abstracts hydrogen mainly from the methyl group of the dimethylamino moiety. The comparison of the initiation ability of polymeric MABP or polymeric DMAEMA with their monomeric forms has also been done and the results indicate that in good solvents P (MABP) has a much higher initiation ability than that of monomeric MABP, but monomeric DMAEMA and P (DMAEMA) display almost the same initiation ability. In poor solvents, the initiation ability of P (MABP) is not so obviously higher than that in good solvents. The result of UV analysis of P(AN) initiated by the MABP-DMAEMA system indicates that both MABP and DMAEMA not only initiate the photopolymerization of AN, but also enter into P (AN) polymer chains.