It relates to the field of synthetic macromolecular chemistry, and discloses a method for one-step synthesis of thiol-functionalized polyester polyols by organic catalysis. This method uses lactone monomer as reaction raw material, thiol-alcohol as initiator, and diphenyl phosphate as organic catalyst to catalyze and synthesize the thiol-functionalized polyester polyols. The present invention provides a method which is simple, inexpensive, easily controllable and environmentally friendly to prepare thiol-functionalized polyester polyols with the easily available and controllable catalyst. The method can selectively catalyze the ring opening polymerization of lactone to prepare thiol-functionalized polyester polyols using the organic catalyst.