In order to determine the performance of continuous ethanol fermentation in a silicone rubber membrane bioreactor, three types of experiments were carried out. The results show that production inhibiting effect is eliminated by pervaporation, so the ethanol productivity is increased to 3 to 4 times as that in the conventional fermentation process. After condensation, the extracted ethanol concentration is about 4 times as that in the broth. A high concentration of yeast cells is realized by immobilizing of the membrane. However, the proportion of viable cells decreases because of the accumulation of inorganic salts, nonvolatile by-products and aged cells. In order to achieve high ethanol productivity, part of the broth must be removed from the membrane bioreactors.