The luxS gene from quorum sensing system of K. pneumoniae was deleted to study the mechanism of quorum sensing. The yield of 2,3butanediol and several byproducts 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.