Ethyl xanthate ethyl propionate was used as chain transfer agent for reversible addition–fragmentation chain transfer (RAFT) polymerization of methyl methacrylate (MMA). The PMMA-CTA was employed for the preparation of PMMA-b-PS block copolymer by adding the second monomer styrene (St). The PMMA and PMMA-b-PS block copolymer was characterized by FT-IR, ¹H-NMR, GPC, TG and DSC. The results indicate that the PMMA macromolecular chain transfer is copolymerized with the second monomer St and the expected block copolymer is formed. The PMMA-b-PS block copolymer possesses a higher molecular weight and a wider molecular weight distribution. The initial decomposition temperature of the PMMA-b-PS block copolymer is significantly increased, while the glass transition temperature is between that of PMMA and PS.