In this study, the pervaporation separation characteristics were investigated for the iso-propyl alcohol (IPA)-water system using PDMS dense membranes. The ratio, 9:1 and 10:1, of the basic material based on RTV-655 and crosslinkingagent were used to prepare dense membranes at the reaction temperatures, 40, 60, and 80°C. And these resultingmembranes were characterized by pervaporation technique in terms of permeabilities and separation factors for the feedcomposition of IPA 85 wt% at the operating temperatures, 25, 35, 45, and 55°C. Typical results of permeabilities 148 g/m²⋅hr at 55°C for 9:1 membrane and the selectivity 17 at 55°C for 10:1 membrane were obtained, respectively.