Imide-oligosiloxanes hybrid nanocomposites (Imide HYBRIMER) were synthesized and their unique structure and thermal and mechanical properties were investigated. Imide HYBRIMER was made by reaction with nano-sized amine oligosiloxane (AO) and dianhydride, where oligosiloxane moieties were cross-linked by imide bonds to form three-dimensional nanocomposite. The AO were prepared from condensation reaction with aminopropyltirmethoxysilane (APTS) and diphenylsilanediol (DPSD) under base catalysts without water and solvents. The preparation of imide HYBRIMER was completed through the thermal imidization of amic acids, which were formed by reaction with amines groups in the AO and two different kinds of dianhydrides. The imide HYBRIMER were stable up to 400°C and thermal expansion coefficients measured by thermo-mechanical analysis (TMA) were varied from 33 to 80 ppm/°C. Higher thermal stabilities and mechanical strengths could be obtained by incorporating siloxane moieties in hybrid nanocomposites. The imide HYBRIMER, which has three dimensional network, could induce very low birefringence about 0.003, which was lower than that of linear typed polyimides.