Poly (ether-ester) modified silicone oil was synthesized by fourteen acid allyl polyether ester and low hydrogen silicone,using H2PtCl6 as catalyst.The chemical structure was characterized by IR.The effects of reaction temperature,time and the molar ratio of reactants on the hydrosilation reaction were investigated. Surface tension of poly (ether-ester)modified silicone solution at different mass concentration was determined. The defoaming performance of the defoamer emulsion was studied.The results showed that:reaction temperature was 85℃,reaction time was 6h,molar ration of n(C=C):n(Si-H) was 1.30:1, the conversion rate of Si-H could reach 87.6%.The defoaming time of the emulsion was 5s,bubble restrain height was 300mL.