The Paleoproterozoic Badu Group in southwestern Zhejiang Province is the oldest metamorphic basement in the Cathaysia block, and its metamorphic grade was previously considered to be only of amphibolite facies. Recently, pelitic granulite with the typical mineral assemblage of garnet+sillimanite+perthite+antiperthite+biotite was discovered in the Al-rich gneiss of Suichang area. According to petrographic observation, micro-mineral composition and calculating results from garnet-biotite thermometer and GASP barometer, three stages of metamorphism were recognized in the pelitic granulite. The early prograde metamorphic stage (M₁) was detected on the basis of inclusions of biotite, muscovite and sillimanite in garnet. The peak metamorphic stage (M_2-3) is characterized by the presence of garnet, biotite, sillimanite and ternary feldspar, with a probable pT condition of 0.6～0.7 GPa at ca. 800～850℃. The post-peak retrograde metamorphic stage (M₄) was recognized according to the mineral assemblage of biotite, garnet, fresh plagioclase and muscovite, with a pT condition of 560～590℃ and 0.25～0.33 GPa. The garnet from the pelitic granulite developed both diffusion zoning and symplectite of plagioclase related to the lowering of temperature and pressure, respectively. A clock-wise pT path has been constructed for the pelitic granulite which is consistent with the thinning process of the thickened continental crust.