A novel hybrid film composed of copolyimide with hydroxyl group, silica and gamma-glycidyloxypropyltrimethoxysilane (CPI-OH/SiO2/GOTMS) was prepared by the sol-gel process based on hydrolyzed tetraethoxysilane (TEOS) under acidic condition. GOTMS, as the coupling agent, and hydroxyl group in PI chain were used to improve the compatibility between the PI and SiO2. The components, morphologies, and mechanical properties of the hybrids were investigated by FTIR, UV-vis, SEM, stress-strain tests, and DMA. The results showed that SiO2 particle size significantly decreased, fractured cross sections of hybrid were rougher, and the surfaces of spherical SiO2 particles were more widely covered by PI component. The tensile mechanical properties of hybrids increased when adding GOTMS. The critical points of maximum tensile strength and elongation at break move from 11 to 16 wt % SiO2 content. DMA results showed that the storage moduli of hybrids with GOTMS, when above 260 degrees C, were obviously higher than those without GOTMS; the tan delta transition temperature of hybrid films went up from 317 to 337 degrees C. It suggests that chemical interaction between CPI-OH and SiO2 is formed and the PI molecular mobility is restricted by the chemical interaction. (c) 2007 Wiley Periodicals, Inc.