Experimental results of the influence of diffusional resistance in the liquid phase on the pervaporation of binary mixture water-isopropanol on the membrane PERVAP 10005 has been presented. The effect of the flow hydrodynamic, composition and temperature of the liquid phase on the permeate flux, selectivity and coefficient of pervaporation was investigated. The model of the process was developed which enables one to calculate the mass transfer coefficient for a flat membrane module in the laminar flow.