Asymmetric microbial reduction of acetyltrimethylsilane to (－)-1-trimethylsilyl-ethanol with immobilized Saccharomyces cerevisiae cells in water/organic solvent biphase system was studied. The effects of shake speed, the hydrophobicity of organic solvent, volume ratio of water phase to organic phase, pH of aqueous phase and reaction temperature on the initial reaction rate, maximum yield and enantiomeric purity of the product were systematically explored. All the factors mentioned above have important effects on the reaction. n-Hexane is found to be the best organic solvent for the reaction. The optimum shake speed, volume ratio of water phase to organic phase, pH and reaction temperature are 150 r/min, 1/2, 8 and 25～30℃ respectively for the reaction, under which the maximum yield and enantiomeric purity of the product are as high as 96.8% and 95.7%(ee) respectively.