Abstract: Glutamate decarboxylase( GAD) is a key enzyme involved in the biosynthesis of γ- aminobutyric acid.In this study,a recombinant Bacillus subtilis expressing glutamate decarboxylase was constructed through genetic engineering,and fermentation conditions for production of GAD were optimized by single- factor test,orthogonal test and response surface methodology,and the conditions were as follows,sucrose 23.5,soybean meal 10,ammonium acetate 8.5,potassium dihydrogen phosphate( KH2PO4) 4.1,magnesium sulfate heptahydrate( Mg SO4·7H2O) 0.5,initial p H7.0 and 37℃ of culture temperature. Compared with the initial 0.143 U / m L,GAD activity was incresed by 188.8% and reached 0.413 U / m L under the optimized conditions. This study would contribute to the subsequent development of γ- aminobutyric acid production process in B.subtilis,for the sake of bypassing the safty issue related to Escherichia coli and high cost associated with Lactic acid bacteria during γ-aminobutyric acid production nowadays.