Imidodiphosphorimidate　(IDPi)　is　demonsatreted　as　a　novel　and　efficient　acid/base　bifunctional　organocatalyst　for　controlled/living　ring-opening　polymerization　of　lactones,　which　delivered　the　metal-free　poly(delta-valerolactone)　and　poly(epsilon-caprolactone)　with　excellent　control　over　the　molecular　weight　and　narrow　dispersity　at　a　low　catalyst　loading　under　mild　conditions.　NMR　and　MALDI-TOF　characterizations,　kinetic　study,　and　chain　extension　experiment　suggest　a　well-controlled/living　nature　of　the　current　ROP　of　lactones　catalyzed　by　the　IDPi　catalyst.