Pure ferrous ion and benzene diazonium fluoroborate will not initiate the poly-merization of acrylonitrile，while a small amount of copper ion is present，the poly-merization of acrylonitrile will proceed smoothly and its rates of the polymerization will obey the following relationship：The polymerization of acrylonitrile can be initiated by p-nitrobenzene diazonium fluoroborate with the pure ferrous salt containing no copper ion and its rates are affect-ed Very slightly by adding small amount of copper ion．When the concentration of fer-rous ion or the rate of the polymerization is high in these systems，the rates of poly-morization will be proportional to [Fe++]．Results support that the redox reaction is taken place between p-nitrobenzene diazonium salt and ferrous ion．The effects of substituting groups on the para position of benzone diazonium flue-roborate were discussed．