Hydrophobically modified polyester was synthesized via copolymerization between hydroxy-fluorosilicone polymer (FGX) and bis(2-hydroxyethyl) terephthalate (BHET), which was named as CMPET. The relations between surface properties of CMPET and FGX viscosity and dosage were studied by contact angle measurements. An optimized synthesis route was determined. b-CMPET with better hydrophobic property was obtained by adding polytetrafluoroethylene (PTFE) into CMPET. A full characterization were given to both CMPET and b-CMPET, including (1)H-NMR, ESCA, mechanical properties, water absorption, contact angle and surface energy analysis. It was found that chemical bondings were formed between FGX and BHET in c-CMPET via copolymerization. The addition of 12% FGX with viscosity of 2000CP after the system pressure reached the low pressure for 20 min is an optimum condition. The modified polyester (CMPET-12) shows the best hydrophobic effect. Blending a certain amount of PTFE powder with low-surface energy can further enhance the hydrophobic properties of CMPET, due to a strong tendency of PTFE migrate to the sample surface together with organic fluorine-silicon segments. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 120: 2760-2766, 2011