The migmatitic granite-gneiss dome has the following characteristics: 1 .It looks elliptic in plane and funnel-shaped in profile, being 50一100 km long and 20-40 km wide. 2 .With the gradual intensification of metamorphism, migmatization and granitization from the low-grade area to the center of the migmatitic granite- gneiss dome, there appear in. turn sericite-chlorite zone, biotite zone, garnet zone, staurolite zone, kyanite （andalusite) zone, sillimanite-cordierite zone, migmatite zone and migmatitic granite-gneiss dome, indicating an increase in temperature from 400℃to 700℃ and drop in pressure from 0.85 GPa to 0.35 GPa. 3·From the low-grade area to the center of the dome, a progressive sequ- once of metamorphic structures can be observed, which finds expression in a series of prograde folds and schistosities. The nearer the rocks are to the center of the dome, the higher grade of tectonism and more deformation they have undergone. 4 .The migmatitic granite-gneiss dome consists mainly of biotite migma- titrc granite-gneiss and leuco-migmatitic granite-gneiss intercalated with migma- tined mica schist. In such aspects as attitudes, rock types, modal abundances, fabrics, petrochemistry and rare earth elements, there exist continuous and gradual variations from phyllite mica schist, migmatized mica schist to biotite migmatitic granite-gneiss and from metamorphic rhyolite, leptite, migmatized leptite to leuco-migmatitic granite-gneiss, suggesting that the two sorts of mig- matitic granite-gneiss are genetically related to meta-petite and metamorphic acid volcanic rocks respectively and should attribute their formation to m}ta- morphism, migmatization and granitization. The thermal dome of progressive metamorphism, the structural dome of progressive deformation and the migmatitic granite-gneiss dome constitute a thermal-structural-gneiss (TSG) trinity dome. The unified temporal-spatialevo- lutionary process of progressive metamorphism, deformation, migmatization and granitization implies that the formation of the TSG dome is attributed to heat fiow upward gushing of fluids rich in K, Na and Si, and differential diapric uprise around the center of the regional thermodynamic anomaly.