Abstract: Waterborne epoxy resin(EP)/polyurethane(PU) composite polymers were prepared from anionic polysiloxane modifying terpene-base epoxy resin based polyol dispersions(ASTP) and hydrophilically modifying hexamethylene diisocyanate(D80). The silicon concentration on the uppermost surfaces of the composite polymers was higher than that at the polymer-substrate interfaces. This result implied that the hydroxypropyl terminated polydimethy-siloxane(HTPDMS) segments enriched at the polymer-air interface and formed the hydrophobic film surface. When the amount of the HTPDMS reached 10% by weight based on the weight of ASTP, siloxane content on the uppermost surfaces was saturated and the contact angle increased to about 95°. Due to the good thermal stability of siloxane segment, the introdution of HTPDMS to the polyurethane improved the thermal stability of composite. However, due to the low glass transition temperature of siloxane segment, the attachment of HTPDMS to the polyurethane decreased the glass transition temperature of the composite, and the formation of microphase separation between HTPDMS segment and the resin matrix also led to a decrease of glass transition temperatures of the composite polymers.