To find a high γ-aminobutyric acid-producing lactic acid bacterium, more than 110 strains of lacto-bacillis isolated from Chinese fermented foods and astrointestinal tract of chickens were screened using thin-layerchromatography and colorimetric methods with glutamic sodium as substrate. The results showed that strain S6-4 exhibited high GABA-producing ability with 1.98g/L, which was identified as L. brevis by API 50 CHL kit and 16 S rDNA sequencing analysis. The factors on transformation of GABA ability of strain S6-4 were analyzed and finally determined as follows: MRS medium with beef extract and yeast extract as nitrogen source, subsequently added 1mg/L（w/v） VitB6 and VitC as growth factor, initial pH was 6.5, cultured for 36 h under the condition of 27℃, the GABAyield reached 4.05g/L and increased by 105%.