: Among various membrane processes, pervaporation is an effective process for separating the species of liquid mixtures particularly azeotropic and close-boiling mixtures. The membrane is the most important and key part of the pervaporation process and therefore it is useful to do some modification, including making mixed matrix membranes, to improve membrane propertiessuch as mechanical and thermal resistance as well as separation characteristics namely permeation flux and separation selectivity. The subject of the present research work was synthesis of MMMs using poly(vinyl alcohol), which is widely used polymers for preparing pervaporation membranes, cross-linked with fumaric acid and improving membrane properties by adding silica nano particles to the membrane matrix. To this aim, properties of the MMMs were studied by adding different amount of nano-silica particles to PVA membranes matrix. The incorporation of nano particles into the polymer matrix was confirmed with FT-IR analysis by the observation the peak related to SiO 2 . According to mechanical tests, increasing the nano particles loading in the polymer matrix improved the mechanical stability of the membranes. For example when 20 percent of nano-silica was added to the polymer matrix, tensile Strength at break was enhanced from 85MPa for pure PVA to 124MPa for the MMM.The synthesized MMMs were used for pervaporation dehydration of water/isopropanol mixtures to investigate the effects of nano-silicaincorporation in the polymer matrix on its PV performance. The pervaporation results at constant feed concentration showed simultaneous enhancement of flux and selectivity upon adding nano-silicato the membrane matrix, so that for a feed containing 10 wt.% water, at 60°C, the flux and selectivity for the MMMs containing 20 wt.% of nano-silica were 0.436 kg/m 2 .h and 763, respectively. At the same feed concentration and temperature, these values were 0.153 and 277 for the membrane containing 5 wt.% nano-silica. It is worth mentioning that the most important achievement of this work was simultaneous enhancement of the separation characteristics by adding nano-silica particles. In addition toto the effect of nano particles content, effects of operating conditions such as feed composition and temperature on the membrane performance were studied. It was observed that increasing in the feed concentration and temperature led to increasing flux and selectivity decline. Keywords: poly (Vinyl Alcohol), Mixed Matrix Membrane, Nano-Silica, Pervaporation, Isopropanol