Garnet group is one of the major rook-forming minerals in dark mafic rocks, gxanulite and gneiss of the Archean metamorphic complex in Liaoxi- Chifeng area. It is of pyrope-almalndine series containing lots of grossular molecules accordiazg to electron microprobe analyses and is close to alman- dine according to infrared absorption spectra. Mossbauer spectra of garnets show that the increase in Fe3+ coxltent will lead to further deformation of six-coordinated polyhedra in garnets .There exists positive correlation between the cell parameter so and the Ca2+ content of garnets .Chemical composition and structural relationship with other coexisting minerals suggest that garnets are products of granulise facies metamorphism under the condition of temperature 700-840℃` and pressure 0.85-1.10 GPs. The reactions causing the foxmation of garnets are complex, which include the temperature rising dehydration reaction of hornblende and plagioclase and the sliding reaction from the hypersthene + plagioclase assemblage to the garnet + clinopyroxene assemblage.