Among the various membrane processes, pervaporation is an effective process for separating the species of aqueous mixtures particularly azeotropic and close-boiling point mixtures. Because the membrane is recognized as the most important part of the pervaporation process, the correct choice of polymer and any modification is essential to acquire membranes with better separation properties such as permeation flux and selectivity. Among different polymer materials, poly (vinyl alcohol) is the most considered polymer due to the high chemical and mechanical resistance and its hydrophilic nature. The limitation of this polymer is its high swelling in aqueous solutions that can be prevented by crosslinking. In this study Glutaraldehyde is used as cross linking agent and Hydrochloric acid as the catalyst of this reaction. The creation of acetal and ether functional groups of the reaction of Glutaraldehyde and poly (vinyl alcohol) was confirmed by FT-IR. In order to increase the hydrophilic nature of membrane Lithium bromide which is a hydrophile salt was used. Addition of Lithium bromide increased crystallinity and the hydrophilic nature of membranes. To investigate the effect of Lithium bromide content on PVA membrane, different amounts of this salt from 0.05 wt. % to 1 wt. % was used for preparation of membranes. The results of pervaporation tests revealed that by increasing LiBr to 0.5 wt. % the flux increases, however by increasing Lithium bromide from 0.5 wt. % to 1 wt. %, the flux decreases. But the selectivity of membranes increases by increasing the content of Lithium bromide. According to DSC and XRD curves, PVA-0.5 LiBr has the lowest crystallinity. As the increased crystallinity decreased free volumes, the highest permeation flux in PVA-0.5 LiBr is to be expected. Pure PVA membrane has the selectivity and flux of 76 and 0.1049 respectively, while the addition of 1 wt.% LiBr increases selectivity and flux to 779 and 0.1063 . In addition of the effect of content of Lithium bromide, the effect of feed temperature was also investigated. It was observed that permeation flux increased with increasing temperature but selectivity was decreased. Arrhenius plots were drawn to compute the activation energies for the total permeation flux. As the temperature dependency of flux for a membrane can be indicated by the magnitude of activation energy, so the temperature dependency of membrane containing 0.5wt. % LiBr is the fewest. Keyword: poly (vinyl alcohol), lithium bromide, pervaporation, crystallinity.