The properties of glutamate decarboxylases(GADs) produced by Lactobacillus fermentum, Lactobacillus plantarum and Lactobacillus brevis were studied. The effects of temperature, pH, pyridoxal phosphate(PLP) concentration and GAD concentration on GAD activity were analyzed. Besides, the Michaelis-Menten constants of the high-activity GADs from lactic acid bacteria were determined. The results showed that the optimum temperature and pH of GADs from three lactic acid bacteria were 40℃ and 4.5 respectively. The maximum enhancement of GAD by PLP was achieved when PLP content was 0.1mol/L. The Km and Vmax of L. fermentum GAD were 0.05215mmol/L and 2.08μmol/min respectively. And for L. brevis GAD, the Km and Vmax were 0.0243mmol/L and 1.01μmol/min respectively.