The fatty acid compositions of Saccharomyces cerevisiae and its organic solvents tolerated mutants Y-c-8 and B-g-5 were determined and compared. It was found that the amount of long chain unsaturated fatty acids in the organic solvents tolerated yeast mutants increased due to their adoptability to the harmful environment. As a theoretical research on the toxicity mechanism of organic solvent to microorganisms, this study may promote the industrial application of microbe whole cell biocatalysis in organic solvents.