Reverse atom transfer radical polymerization of styrene initiated by benzoyl peroxide(BPO) or potassium persulfate(KPS) in emulsion systems with phenanthroline as ligand and sodium lauryl sulfate as surfactant was studied．For the BPO initiator system

the good control over the polymerization of styrene was observed when both CuBr and CuBr2 were simultaneously introduced into the reaction system．In this case

the fast initiation could be expected as a result of the quick redox reaction of CuBr and BPO

and the addition of CuBr2 at the beginning of polymerization could further improve the controllability of the polymerization．For the polymerization initiated by KPS

the pH value of the reaction medium played a crucial role in affecting the polymerization rate of St which increased with the increase of the pH value of the medium．The particle size and particle size distribution of the synthesized polystyrene with BPO or KPS were measured

and found to be quite different．