Graphene oxide (GO) was firstly prepared from modified Hummers method, then silanized GO is reduced in situ emulsion using aqueous ammonia to achieve reduced graphene oxide/waterborne polyurethane (KRGO/WPU) nanocomposites.The effect of KRGO content on the fracture morphologies, mechanical performance, thermal stability and water-retardant properties of KRGO/WPU composites was investigated by FT-IR,XRD,TEM, SEM, universal testing machine, TG etc. The results showed that the thermal stability of KRGO/WPU is obviously higher than pure WPU, and the effect of thermal stability decreases with the increase content of KRGO. When the KRGO is up to 1.0wt%, the tensile strength of the composite reached its maxmum 20.2 MPa, 187.1% higher than that of pure WPU.However, the effects were less pronounced at high content (2.0wt%) due to the agglomeration of KRGO particles.In addition, the stability and water-retardant property of KRGO/WPU composites is obviously improved compared with pure WPU.