||Living radical polymerization (LRP) has opened a new era for preparing various polymers having a pre-determined molecular structure. Several techniques have been proposed for LRP including nitroxide-mediated polymerization (NMP), addition-fragmentation chain transfer (RAFT) method, and atom transfer radical polymerization (ATRP). In this study, a novel addition-fragmentation chain transfer agent (iniferter) bearing di-thioester group is synthesized and applied to conventional dispersion polymerization of styrene in ethanol medium including poly(N-vinylpyrrolidone) (PVP) stabilizer with various amounts of the iniferter and optionally with a conventional initiator, AIBN at 70 oC. Monomer conversion, molecular weight evolution, molecular weight distribution, and final particle size are characterized at various conditions. As the iniferter concentration increases, higher conversion, lower molecular weight and molecular weight distribution are obtained. A linear relationship between the molecular weights and the polymerization time is observed, showing the nature of living radical polymerization. In addition, it is found that the addition of iniferter significantly lowers the molecular weight distribution from 6.1 to ca. 3.0-3.5. Finally, stable PS beads above 1 micrometer in diameter are successfully prepared using this type of iniferter.