A series of polyimide/SnO2 hybrid membranes supported on TiO2/kieselguhr-mullite were prepared from polyimide with a large amount of carboxyl and SnO2 sol via a sol-gel process. The SnO2 phase chemically linked with the polyimide through the pendant carboxyl along the polyimide. The hybrid membranes were highly homogeneous, and when the SnO2 contents reached 15wt% the SnO2 phase was observed as particles with a diameter of 5 nm dispersed in the hybrid membranes . The cross-linking between the SnO2 phase and polyimide effectively enhanced the glass temperature of the hybrid films. With the increasing of the SnO2 contents, the pore sizes of the membranes decreased, and their pore sizes were mainly focused on 3.8, 3.1, 2.8 and 2.4 nm. The hybrid membranes showed higher permeability for H2, CO2, CO and H2O when compared to the pure polyimide. The separation factors of the polyimide/SnO2 hybrid membranes with 15wt% SnO2 content for H2/N2, CO2/N2, CO/N2 and H2O/N2 were 54.1, 30.2, 35.9 and 40.1, respectively.