A complex of polyvinylamine (PVAm) and Cu(II) was synthesized and IR, TG and XPS were employed to examine its structure. It has been found that PVAm-Cu(II) complex/sodium sulfite (Na2SO3) system can be used as initiator of methyl methacrylate (MMA) polymerization. The overall polymerization rate can be expressed as R-P = k[MMA](1.4) [Na2SO3](0.5) [PVAm-Cu(II)](0). The activity of initiator system varies with the composition of PVAm-Cu(II) complex. The polymerization proceeds by a free radical way, and primary radicals are formed by the process of "complexation-hydrogen transfer" between PVAm-Cu(II)/ Na2SO3/MMA system. The copolymerization of MMA and styrene (St) with PVAm-Cu(II)/Na2SO3 system as initiator differs from the conventional radical copolymerization. (C) 2003 Elsevier Science B.V. All rights reserved.