We disclose an efficient catalyst system of commercial ureas/alkoxides for the challenging ring-opening polymerization (ROP) of bioderived nonpolymerizable gamma-butyrolactone (gamma-BL). This effective polymerization can not only be performed under mild conditions like bulk polymerization, higher monomer ratio, and elevated temperature (-20 degrees C comparing to -40 degrees C), but also obtains high-molecular-weight poly(gamma-butyrolactone) (P gamma BL) (M-n up to 68.2 kg/mol). To our knowledge, this is a big progress in the research area of ROP of gamma-BL, which provides a promising prospect for the industrial-scale methodology of P gamma BL production. Structural analysis including NMR and MALDI-TOF, along with mechanistic computational studies based on DFT calculations, show that urea anion acts as a bifunctional catalyst, which activates the alcohol initiator and gamma-BL before obeying an anionic polymerization. Furthermore, the catalytic activities of ureas/alkoxides systems have been optimized using the ureas with electron-donating groups which are proved to have lower activation barrier by computational calculation.