Yindian—Malong fault zone is one of the most important ductile shear zone in Tongbai—Dabie southern margin.It is the rock stratigraphic unit boundaries in Tongbai—Dabie mountains. It is also the product of the collision of Yangtze plate and the North China plate.It has prominent significance in Tongbai—Dabie orogeny belt.By comparative analysis of the lithology and Microstructure and finite strain measurement and so on between eastern and western section of Yindian—Malong fault zone, we can find that Yindian—Malong fault is a dextral shear zone ,despite there is a little difference beween its eastern part and western part.It has an abatement—transfer effect on the collision stress between Yangtze plate and Tongbai—Dabie orogeny belt.It is the strongest band of plastic flow,and acts as a lubricant between Tongbai—Dabie and Yangtze plate.