Improving properties of polyurethane (PU) elastomers have drawn much attention. To extend the properties of the modified PU composite, here a new method via the reaction of poly(urethane-imide) diacid (PUT) and silane-modified epoxy resin (diglycidyl ether of bisphenol A) was developed to prepare crosslinked poly (urethane- imide)/epoxy/silica (PUI/epoxy/SiO2) hybrids with enhanced thermal stability. PUT was synthesized from the reaction of trimellitic anhydride with isocyanate-terminated PU prepolymer, which was prepared from reaction of polytetramethylene ether glycol and 4,4'-diphenylmethane diisocyanate. Thermal and mechanical properties of the PUT/epoxy/SiO2 hybrids were investigated to study the effect of incorporating in situ SiO2 from silane-modified epoxy resin. All experimental data indicated that the properties of PUT/epoxy/SiO2 hybrids, such as thermal stability, mechanical properties, were improved due to the existence of epoxy resin and SiO2. (C) 2010 Wiley Periodicals, Tnc. J Appl Polym Sci 117: 3722-3728, 2010