Block copolymers D,L-Polylactide-b-poly(poly(ethylene glycol) methyl ether acrylate) (D,L- P(LA)-b-P(PEGMA)) were prepared via ring-opening polymerization and reversible addition fragmentation chain transfer (RAFT) polymerization. The block polymers generated in the reaction reveal the living behavior with the molecular weight increasing with time. The copolymer D,L-P(LA)200-b-P(PEGMA)225 was synthesized successfully with D,L-P(LA) macro-RAFT agent, and was self-assembled in an aqueous environment, leading to the formation of self-assembly micelles. A distinct critical micelle concentration (CMC) was observed of the self-assembly system. The size of it was characterized by both DLS and TEM.