A series of starch-graft-poly (methyl methacrylate) (S-g-PMMA) copolymers were prepared by single electron transfer living radical polymerization (SET-LRP) at molecular level under mild conditions. The successful grafting polymerization was confirmed by FT-IR and H-1 NMR spectroscopies. The hydrolysate of S-g-PMMA via acid-catalyzed hydrolysis proved to be a mixture of 1-arm, 2-arm and 3-arm polymers by MALDI-TOF measurements. Furthermore, the micelles formed by S-g-PMMA copolymers in water were studied at various conditions by SEM, TEM and DLS measurements. The results indicate that the sizes of micelles decreased following the order of the common solvents of 1,4-dioxane, tetrahydrofuran, acetone and acetonitrile, and also increased with the increase of initial copolymer concentrations, addition rate of water and length of grafted chains.