Mylonites in the Dabie orogen are fault and shear zone related rocks formed under metamorphic conditions. They can be divided into greenschist, amphibolite, granulite, and eclogite facies mylonites. The main criterion for identifying the mylonites in the Dabie Mountain is the ductile (plastic) deformation of index minerals of the constituent metamorphic facies. This is clearly different from the former definition and description of mylonite. Formation epoch of the mylonites in the Dabie Mountain was approximately the same as (or a little later than) that of peak metamorphism of their host rocks. From older to younger, the series follows the order eclo- gite facies mylonite→granulite facies mylonite →amphibolite facies mylonite→greenschist facies mylonite. According to lithology and texture, the mylonites can be further divided into second and third subclasses if necessary. Former mylonites of eclogite and granulite facies are always superimposed by the later facies and show the appearance of amphibolite or even greenschist facies mylonites; the earlier formed mylonites are thus preserved as relics in their retrograded products. Mylonites in the low-grade metamorphic rocks in southern and northern Dabie Mountain only experienced the metamorphic history of greenschist and amphibolite facies mylonitization during the Paleozoic-Triassic period.