3-aminopropyltrimethoxysilane, as a kind of modifier, was grafted on the surface of graphene nanosheets. The morphology of this kind of APTMS-GO and its properties were investigated by FT-IR, TG, XRD, Raman, AFM and TEM, respectively. APTMS-GO was well dispersed into dispersing agent and then added to the prepolymer to get a series of hybrid emulsion by in-situ polymerization, with the addition of APTMS-GO from 0.00 to 0.55wt.%. The properties, including mechanical property, thermal properties and hydrophobicity, of the APTMS-GO/WPU films, were tested. The cross-sectional morphology and emulsion particle of nanocomposites were also observed by FESEM and TEM, respectively. The results indicated that tensile properties of this hybrid film incorporated by the APTMS-GO via in-situ polymerization were significantly improved, with the tensile strength increasing from 10.13MPa to 28.96MPa. Thermal properties showed that adding 0.22wt.% APTMS-GO into the polymer matrix could enhance the initial thermal degradation(5% weight loss) temperature from 245 to 279oC. Hydrophobicity tests indicated that water contact angle (WCA) of the composite increased from 71.3° to 91.28° with increase in APTMS-GO content of the hybrid emulsion.