The miscibility, transesterification and formation of ringed spherulites in blends of poly(epsilon-caprolactone) (PCL) with butylene terephthalate-epsilon-caprolactone (BCL) copolyester have been studied by d.s.c. and polarizing microscope. When the BT contents in copolyesters are below 60%, copolyesters are miscible with PCL. The compatibility between components in the blends has a certain correspondence with the weakening of PCL crystallization ability in the blends. The transesterification can easily occur in the blends at 530 K. The transesterification depends on the miscibility between components and the BT content of the copolyesters, though the BT content plays a more important role in the trans-reaction. Both copolyesters and transesterified copolyesters can evidently improve the formation of ringed spherulite in PCL/BCL copolyester blends.