Polystyrene grafted with poly（methyl methacrylate（PS-g-PMMA）has been achieved via atom transfer radical polymerization（ATRP）methodologyThe grafting reaction of methyl methacrylate（MMA）was initiated from the chloroacetyl groups on the chloroacetyl styrenedivinylbenzene copolymer microspheres（PS-acyl-Cl）with CuCl/CuCl2 and N，N，N′，N′-tetramethyl ethylenediamine（TMEDA）complex as catalystThe influences of the catalyst，reaction temperature，and the amount of ligand and solvent on the grafting reaction were investigatedUnder the optimized conditions，satisfactory grafting yields（up to 687% within 15 h）were obtained using PS-acyl-Cl microspheres with 3.44 mmol.g-1 of chloroacetyl groups，and at the same time，the grafting reaction showed a firstorder kinetics nature（k=5.13×10-5 s-1）.The PS-g-PMMA microspheres with different grafting arm lengths were obtained by varying the reaction conditions，which are expected to be used as weakacid ion exchange resin with high loading amount after being hydrolyzed，or as flexible immobilization carrier for enzymes after further functionalization.