Abstract: According to the study of the characteristics of microscopic and supermicroscopic deformation of the Fengyang-Fengtai nappe of the Ying- shang-Fentai area,Huainan coalfield,Anhui,it has been revealed that the nappe is a shallow-and middle-level superimposed nappe and that the main deformation of the nappe is brittle.The nappe was formed in the late stage of the Indosinian movement and best developed during the early Yanshan- ian.In the kate stage of the Yanshanian and the early stage of the Hima- layan movement,the motion of the nappe gradually stopped and then the nappe was reformed.The values of the ancient tectonic stress obtained from calculations of the dislocation density and size of the sub-grains show that the nappe was formed and developed in the tectonic environment with a high stress and high strain rate.