The luxS gene from quorum sensing system of K. pneumoniae was deleted to study the mechanism of quorum sensing. The yield of 2,3butanediol and several byproducts in the K. pneumoniae wild type and its luxS mutant was compared. Results showed that the yield of 2,3-butanediol in the luxS mutant was 47.75% higher than that in the production with the same concentration of glucose. The concentration of the by products including succinic acid, lactic acid and ethanol was obviously decreased.