The amount of GS in Sulfolobus acidocaldarius can be regulated up by different growth medium, this difference is regulated at mRNA level. The GS was purified by DEAE-Sepharose and Sephacryl S-300 to homogeneity. The molecular mass was determined to be dodecameric protein (630 ku) composed of identical subunits of 53 ku. The optical pH of this enzyme is about 7.3, the optical temperature of both γ-glutamyl transferase activity and biosynthetic activity is 90℃, the Arrhenius plots show that the active energy is 47 kJ/(mol·K) for transferase activity and 29 kJ/(mol·K)(40～55℃),10 kJ/(mol·K)(55～90℃) for biosynthetic activity respectively. GS was stable at 78℃ in the presence of Mn²⁺, the K_m values were 3.5 mmol/L, 1.3 mmol/L, 0.5 mmol/L and 0.24 mmol/L for hydroxylamine, glutamine, ADP and Mn²⁺ respectively. The inhibitors experiments showed that the catalytic activity of GS from Sulfolobus acidocaldarius unlike that of others was regulated solely by feed-back inhibition through L-alanine and glycine, the normal inhibitors such as L-tryptophan, L-histidine and 5′-AMP have no inhibitory effect on this enzyme. L-alanine and glycine have shown synergistic effect on catalytic activity of GS. The post-translation modification like other gram positive bcteria is not regulated by adenylylation/deadenylylation system.