The present disclosure relates to a method for modifying polyester by a swelling agent combined with cutinase, belonging to the technical field of textile processing. According to the method, a phenol solution or an o-vanillin solution is used as the swelling agent to perform swelling treatment on the polyester, and combined with a Humicola insolens cutinase solution to perform hydrophilic modification on the polyester, which not only significantly improves the release amount of hydrolysates, but also reduces the fabric mass loss compared with the traditional chemical modification method.