The　tacticity　of　vinyl　polymers　is　a　key　factor　affecting　the　properties　of　materials.　Recently,　organic　Bronsted　acids　have　been　demonstrated　as　effective　catalysts　for　the　development　of　highly　stereoselective　cationic　reversible　addition-fragmentation　chain　transfer　(RAFT)　polymerizations　of　vinyl　ethers,　in　which　the　use　of　RAFT　agents　could　allow　the　control　the　molecular　weight　and　tacticity　of　polymer　products　simultaneously.　However,　the　effect　of　RAFT　agents　on　the　tacticity-regulation　remains　elusive　and　lacks　of　investigation.　In　this　study,　we　synthesized　four　types　of　RAFT　agents　and　evaluated　their　influence　in　the　stereoselective　cationic　polymerization　of　isobutyl　vinyl　ether　in　the　presence　of　PADI　as　a　Bronsted　acid　catalyst,　which　unveils　that　the　Z　group　of　RAFT　agents　could　not　only　affect　the　polydispersity　of　the　products,　but　also　exert　a　profound　effect　on　the　stereoselectivity.　After　extensive　screening　of　the　RAFT　agents,　high　stereoregularity　(isotacticity,　90%　m)　was　obtained　when　using　dithiocarbonate　ester-type　RAFT　agents　with　a　benzyloxy　Z　group.