Hybrid polyurethanes with double-decker silsesquioxane (DDSQ) in the main chains were synthesized using castor oil and isophorone diisocyanate (IPDI) as feedstock. Double-decker octaphenylsilsesquioxanetetraol (DDSQ) was prepared and characterized by H-1 NMR and MALDI-TOF-MS. Meanwhile, FTIR, TGA, DSC, SEM, UV-Vis spectrophotometer, tensile test techniques and static contact angle were also carried out to investigate the structures and properties of the hybrid polyurethanes. The DDSQ-containing hybrid polyurethanes exhibited improved thermal stability in terms of thermogravimetric analysis (TGA). DSC analysis demonstrated that the hybrid polyurethanes with DDSQ displayed enhanced glass transition temperature. According to the results of SEM and UV-Vis spectrophotometer, the aggregates of DDSQ were dispersed homogeneously in the hybrid polyurethanes matrix. With the inclusion of DDSQ, the hydrophobicity of the hybrid material was significantly improved as the results of the static contact angles revealed.