Abstract: A new type of polyester polyether copolymer hydrophilic finishing agent was synthesized by adding modifying monomer with Sodium-5-sulfoisophthalic acid dimethyl ester (SIPM). The effect of these factors such as the dosage of SIPM、temperature and time of polycondensation and amount of catalyst on solubility in water or hydrophilic properties of finishing agent were studied, the synthesis reaction conditions was optimized, the structure and properties of finishing agent was studied by using FTIR、Thermal gravimetric analyzer and X-Ray diffraction, and the application properties of finishing agent were studied. The results indicate that when the molar ration of SIPM to ester(total amount of SIPM and DMT) is 30%, polycondensation temperature is 260℃, time is 45min, mass fraction of catalyst to ester is 0.20%, the water solubility, hydrophilicity and washing durability of finishing agent are good. TR analysis indicates that finishing agent has polyester polyether structure; TG analysis indicates thermal stability of finishing agent is good; XRD analysis indicates that finishing agent is non crystal compound; the hydrophilicity and washing durability of finished fabric with the finishing agent are equivalent with conventional polyester polyether finishing agent A, and the water solubility of the finishing agent is improved obviously.