High-molecular-weight poly(butylene succinate) (PBS) is prepared by the lipase-catalyzed polymerization of dimethyl succinate and butane-1,4-diol via the formation of cyclic oligomers as a new strategy for the green production of bio-based plastics. The cyclic oligomer is first produced by the lipase-catalyzed condensation of dimethyl succinate and butane-1,4-diol in a dilute toluene solution using lipase from Candida antarctica, followed by the ring-opening polymerization of the cyclic oligomer in a more concentrated solution or in bulk with the same lipase to produce PBS with an (M) over bar (w) of 130 000. On the other hand, PBS is produced with an (M) over bar (w) of 45 000 by direct polycondensation.