Abstract: An aqueous polyurethane-polyacrylate hybrid emulsion was prepared by soap-free emulsion polymerization of aqueous polyurethane emulsion with C C double bond modified with acrylic monomer through grafting copolymerization.The morphology and properties of composite particles of the prepared emulsion were studied with IR and TEM etc.The influences of reaction temperature,amount of initiator and agitating rate on grafting copolymerization were investigated.Compared with the unmodified polyurethane emulsion,the particle size of the prepared emulsion became larger significantly and its tensile strength,resistance to water and solvent were remarkably improved.