Abstract: Water-soluble polyester(WSP) was prepared by adding modifying monomer with sulfonic group through copolymerization.And the WSP was characterized by FTIR、DSC and X-ray.The effects of modifying monomer on WSP′s water-solubility and crystallization and thermal property were studied.And the results show that the existence of SO in the molecular chain is confirmed by FTIR,thus proving that SIPE has participated in the copolymerization;and increasing modifying monomer improves the water-solubility of polyester effectively,but it is disadvantageous to its crystallization.