The star-shaped PMA was synthesized by SET-LRP at 30 ℃ with DMSO as the solvent of polymerization,PEBr4 as the multifunctional initiator,Cu0 powder and Me6-TREN as catalytic system.The PMA prepared via SET-LRP was characterized by GPC and 1H-NMR to identify the polymerization mechanism,and the results show that polymer has the perfect functional chain ends and relatively low molecular weight distribution,indicating a controlled polymerization.The effects of water,catalyst and initiator on polymerization were studied;the results show that the H2O content in binary mixtures increases to 20%(volume fraction) led to the kappp increasing from 0.0367 h-1 to 0.2785 h-1.meanwhile the kappp increases in corresponding with increasing catalyst amount or initiator amount,in addition,the w/n of PMA decreases as the amount of H2O,catalyst and initiator increase.