Construction and ethanol production effects of SNF4 gene knockout in Saccharomyces cerevisiae were described in this paper. For knockout of SNF4 gene in S. cerevisiae YS2, a PCR-amplified disruption cassette was used, encoding the short flanking homologous regions to the SNF4 gene and Kan(r) as selectable marker. The SNF4 gene disruption cassette was transformed into S. cerevisiae YS2 through LiAc/SS Carrier DNA/PEG. The positive transformants were grown on G418 plates and verified by PCR. The Kan(r) marker was rescued by transforming plasmid pSH65 into positive transformants and inducing expression of Cre recombinase in galactose-containing medium. Lastly, the YS2-deltaSNF4 strain, in which SNF4 allele gene were completely knocked out, was obtained by repeating the same procedure. The result of anaerobic fermentation showed that ethanol production of the SNF4 gene knockout strain had increased by 7.57 percent as compared with the original strain YS2. The experiment indicated ethanol production could be improved significantly with the approach ofSNF4 gene knockout by Cre-LoxP system.