This thesis focuses on using two kinds of yeast Saccharomyces cerevisiae and Yarrowia lipolytica to produce a special fatty acid cyclopropane fatty acids. How this special fatty acid is synthesized in yeast was studied in this thesis. And based on the synthesis mechanism, an effective metabolic engineering strategy was applied to improve the yield of this special fatty acid. In addition, the yeast Yarrowia lipolytica was engineered to utilise a novel feedstock-methanol as a carbon source in this thesis.