The aqueous solutions of poly(ε-caprolactone-co-lactide)-poly(ethylene glycol)poly(ε-caprolactone-co-lactide) undergoing sol-gel transition as the temperature increases from 20 to 50℃ were successfully prepared.The thermogelling triblock copolymers were synthesized by subtle tuning of the chemical composition and the hydrophilicity/hydrophobicity balance.The sol-gel transition was studied focusing on structure-property relationship.The amphiphilic copolymer formed micelles in aqueous solutions.It is believed to have potential applications in drug delivery and tissue engineering.