The photopolymerization of acrylonitrile (AN) initiated With phenylhydrazine (PHZ) and its derivatives under irradiation of UV light and polymerization initiated with the combination of PHZ and quinone in the absence of light have been studied．Ftom the kinetics of photopolymerization．the initiator and monomer exponents were calculated to be 0.66 th and 2.1th respectively and the overall activation energy was 33.4 kJ／mol for the PHZ-AN system．The mechanism of photopolymerization has been proposed．It shows that the exciplex between PHZ and AN will be formed under ir-radiation and then it decomposes to produce the free radical species for initiation．The occurence of exciplex has been verified through fluorensence spectrometry．On the other hand the mechanism of polymermization in the dark has also been proposed that the charge transfer complex (CTC) between PHZ and quinone will be formed at first and then it decomposes to produce an initiation species．The occurence of CTC has also been verified through．UV spectrometry．