The thermodynamic calculation of dehydration reacton suggests very low activity of H-2O during metamorphic peak of the Archaean granulite complex in the region studied.The a-{H-2O} values for Al|rich gneiss and hypersthene biotite gneiss|granulite in the Taipingzhai region are usually between 0.10 and {0.20},and those in the Louzishan region are {0.15}-{0.25}. The fugacity of O-2 in terms of lgf-{O-2} in the whole region ranges from -8 to -14. The average coefficients of (μ-{H-2O}/X+{Bt}-{Mg}) and (μ-{O-2}/X+{Bt}-{Mg}) in the Taipingzhai region are {-0.293} and {-1.60} respectively,and those in the Louzishan region are {-0.364} and {-1.420}. The activity of H-2O is very low in the whole region, but its values and other data mentioned above are considerably constant from place to place within a given region, even in rocks of different lithological characters. However, they show a certain gradient between different regions. Such characteristics are compatible with the genetic mechanism known as !carbonic metamorphism“ put forward by Newton et al.,i.e., the a-{H-2O} during the peak stage is controlled by permeation of pervasive CO-2 influx of the mantle source,and shows features of external buffering. The thermodynamic calculation of dehydration reacton suggests very low activity of H - 2O during metamorphic peak of the Archaean granulite complex in the region studied. A - {H - 2O } values ​​for Al | rich gneiss and hypersthene biotite gneiss | granulite in the Taipingzhai region are usually between 0.10 and {0.20 }, and those in the Louzishan region are {0.15 } - {0.25 } . The fugacity of O - 2 in terms of lgf - {O - 2 } in the whole region ranges from -8 to -14. The average coefficients of (μ - {H - 2O } / X + {Bt } - {Mg }) and (μ - {O - 2 } / X + {Bt } - {Mg }) in the Taipingzhai region are {- 0.293 and {- 1.60 } respectively, and those in the the Louzishan region are {- 0.364 } and {- 1.420 }. The activity of H - 2O is very low in the whole region, but its values ​​and other data mentioned above are indeed constant from place to place within a given region, even in rocks of different lithological characters. However, they show a certain grad Such characteristics are compatible with the genetic mechanism known as ! carbonic metamorphism ”put forward by Newton et al., ie, the a - {H - 2O during during the peak stage is controlled by permeation of pervasive CO - 2 influx of the mantle source, and shows features of external buffering.