The metamorphic unit Xiaoqingshan Formation in Xiaoqingshan Cu(Au) deposit, Huili County, mainly consists of garnet-sericite phyllite, sericite-quartz phyllite, sericite-quartz phyllite, sericite phyllite, carbonaceous slate and a small amount of albite-actinolite schist. The chloritoid phyllite was considered to be the main component of the formation. Nevertheles, the authors consider that this kind of rock belongs to retrograde garnet-sericite phyllite. The metamorphism of the formation can be divided into three stages: M1, M2 and M3, in terms of the evolution of the texture of the rocks and the relatiohships between the minerals of the rocks.There exists compositional distinction between the core and the rim of the garnets from the garnet_sericite phyllites. Spessartine and almandine make up 29.22%～33.55% and 43.28%～48.86% respectively in the core and 8.65%～17.08% and 60．55%～70．66％ respectively in the rim. Muscovites of two genetic stages, Mus1 and Mus2, have been distinguished. There are three genetic kinds of chlorite in the rocks, formed at three stages respectively.The T and Pconditions of the three metamorphic stages were calculated by means of geothermometers and geobarometers, being 500～550℃, 0.6～0.75 GPa for M1, 400～430℃, 0.3～0.5 GPa for M2, and 280℃， 0.3 GPa for M3. The authors have established the P-T-D path about the metamorphism and deformation of Xiaoqingshan Formation. It seems to be a clockwise one.Based on the T and P conditions of the formation in the area, it is considered that the copper and gold deposit hosted in the formation was replaced by deep-seated Na-, Cu- Au- bearing fluids. It occurred much later than instead of during the metamorphism.