The synthesis of a series of exact graft copolymers composed of poly(methyl methacrylate) (PMMA) backbone chains and PS graft chains up to five in number by a new iterative methodology is described. In this methodology, an in-chain-functionalized A B diblock copolymer (PS-block-P M M A) anion with 3-(tert-butyldimethylsilyloxymethyl)phenyl (SiOMP) group between the PS and PMMA blocks is used as a key building block specially designed to simultaneously introduce both backbone and graft chains. The methodology involves the following three reaction steps in the entire iterative reaction sequence: (1) a living anionic block copolymerization to prepare the above-mentioned in-chain-SiOMP-functionalized AB diblock copolymer anion, (2) a transformation of the SiOMP group to benzyl bromide (BnBr) function, and (3) a coupling reaction of the in-chain-SiOMP-functionalized AB diblock copolymer anion with the in-chain-BnBr-functionalized block copolymer. By repeating the reaction sequence Five times, a series of well-defined exact graft copolymers composed of PMMA backbone chains and PS graft chains up to five in number were successively synthesized. In the graft copolymers herein synthesized, not only the molecular weights of the backbone and graft chains but also the distance between the branch points and the number of graft PS chains are perfectly controlled.