The radical polymerization of a well known functional monomer with hydroxy group such as 2-hydroxyethyl methacrylate (HEMA) in aqueous solution initiated with potas-sium persulfate (KPS) was studied．The polymerization rate and percentage of conver-sion increased as the concentration of KPS increased．Kinetic studies of aqueous solution polmerization of HEMA using [KPS]=2.4×10-3 mol/l was made under different tern-peratures within the range of 35—50℃．and the overall activation energy of polymeriza-tion E．of HEMA using KPS as initiator was evaluated to be 33 Keal／mol (138 KJ／mol)．It was found that the amount of NaSCN played an important role on the peroxide ini．tiated aqueous solution polymerization of HEMA．When the concentration of KPS and H2O2 were equal to 2.4×10-3 and 3.0×10-2 mol/l respectively，NaSCN would act as activator within the range of [NaSCN]/[KPS]=1—10，or [NaSCN]/[H2O2]：0.007—0.7，when these molar ratios increased then NaSCN WOuld always show its inhibition or re-tardation effect and would lower the percentage of conversion． In the case of TBH．NaSCN would act as activator and increase the percentage of conversion．