Plant oil based polyurethanes were synthesized using the mixture of PEPSO and castor oil as raw materials. During the synthesis of prepolymer, different content of double-decker octaphenylsilsesquioxanetetraol (DDSQ-4OH) was introduced into the polyurethane molecular chains through the chemical reaction between OH of DDSQ-4OH and NCO of IPDI. Consequently, a series of emulsion particle distributions and nanocomposites with different DDSQ-4OH contents were acquired and numbers of characterizations were taken to evaluate the properties of these materials such as FT-IR, particle size analyzer, thermal stability, mechanical properties and surface hydrophobicity. TGA results show that the hybrid polyurethanes display both enhanced initial decomposition temperatures (T5% ) and final stable temperature (Tf). Contact angle test results show that with the introduction of DDSQ-4OH, the hydrophobicity of hybrid polyurethanes can be enhanced to some extent. The morphology observed by scanning electron microscopy (SEM) showed that DDSQ-4OH may occur to aggregate with high mass content. Mechanical test results show that with the introduction of DDSQ-4OH, the tensile strength of hybrid polyurethanes can be enhanced to some extent．