A simulator has been developed in order to simulate and to be used to design the pervaporation system for separating organic/water mixtures. This simulator is composed of simulation engine, which includes a modeling of pervaporation system and the numerical analysis, and Graphical User Interface(GUI), which enables us to operate the simulator more easily in the Windows environment. The structure and operation of simulator were clearly presented by demonstrating the full-scale ethanol dehydration process. The performance of simulator turned out to be fairly good through comparing the simulation results with the experimental data of ethanol dehydration pilot tests.