Abstract: In-situ sol-gel method was employed to prepare SiO₂ / PI hybrid films with different silica content s. Themechanical properties at room temperature and cryogenic temperature (77 K) as a function of silica content werestudied. The result s show that the tensile st rength increases with the increasing of silica particles up to 3 % andthen decreases with the increasing of silica content at room and cryogenic temperatures. The cryogenic st rength isobviously higher than that at room temperature. The elongation at break reaches the maximum at 3 % silica contentat room temperature but has no obvious tendency at cryogenic temperature (77 K) . The molecular st ructure andmorphology of the fracture surfaces of hybrid films were analysed by using IR and SEM.