Abstract: The mPEG-G_n-OH_2ⁿ(n=1,2,3,4) was prepared as a macroinitiator through iterative process with the methoxy poly(ethylene glycol) as reactant and then they were used in the ring-opening polymerization of L-lactide (LA) with the catalyst stannous octoate (Sn(Oct)₂).By controlling the feed ratio of LA and macroinitiator,one to four generations of linear-dendritic amphiphilic polymers could be obtained.Then,polymer micelles were self-assembled by dialysis method.The structure of polymers were characterized by ¹H-NMR and GPC,and the aggregations were observed by DLS,SEM and TEM.The results show that the hydrodynamic diameter of micelles are highly influenced by the generations and increased gradually with the increase of the poly (ethylene oxide) (PEO) chains.The size of micelles is verified about 200 to 300 nm.Generally,the shape of micelles is a feature of the hydrophilic-hydrophobic ratio,and the hollow spherical micelles will be formed only when the volume fraction of EO block (φ_EO) is less than 0.35.