Polyethersulfone (PES) and MFI-type zeolite mixed matrix membranes (MMMs) were successfully fabricated by a novel particle suspension impregnating and solution-casting method. The effects of two different membrane preparation methods on the membrane morphology were investigated by scanning electron microscopy; the particle crystal type and distribution were explored by X-ray diffraction and fourier transform attenuated total reflectance infrared spectroscopy. The results showed that the MFI-zeolite particles were successfully synthesized, with particle diameter around 250 nm. Distribution and dispersion of MFI-zeolite particles suspended in the polymer matrix are homogeneous and uniform. The thermal analysis indicates that the glass transition temperature (T (g)) of MMMs is around 230 A degrees C and the initial degradation temperature is up to 460 A degrees C in air. The increment of T (g) compared to the neat PES confirms that the polymer chain rigidification is induced by zeolite particles. The MMMs have been evaluated by the CO2/N-2 separation factor and permeability measured as a function of permeation temperature, the maximum separation factor of the PES/10 % MFI-silica zeolite for the pure gas reaches 35 at 25 A degrees C.