Initiation of acrylonitrile (AN) polymerization in the aqueous solution of sodium thiocyanate by different peroxides was studied．It was found that the structure of peroxides play an important role，if TBH or H2O2 was used as initiator．Addition of small amount of NaSCN would act as activator．the induction period will be shortened as the concentration of NaSCN gradually increases．In case of TBH，percentage of conversion would increase at the same time，So TBH．could be applied to both con-centrated NaSCN aqueous solution polymerization and plain aqueous solution polymeri-zation．In case of H2O2，percentage of conversion would decrease at the same time，so H2O2 could be applied only to aqueous solution polymerization but not to coneen-trated NaSCN aqueous solution polymerization．Within the temperature range of 30-50℃，activation energies of TBH and H2O2 in initiating aqueous polymerization of AN in the presence of some NaSCN were determined to be 63.6 and 66.9 KJ.mol-1 respec-tively．For KPS，the presence of NaSCN would always show its inhibition effect in increasing induction period and lowering percentage of conversion．