Abstract: The middle part of the Chongan-Shicheng tectonic zone is characterized by duc-tile deformation in the early stage and brittle fracturing accompanied by low-temperature quartz veins in the late stage.The early ductile deformation is well represented by the be-haviours of the Youling-Yanai shear zone about 2-5 Km wide as indicated by typical my-lonite associations, lineation, S-C fabrics and S+Z type fabrics of quartz optical axis.Fi-nite strain measurements show a maximum shear strain of about 1.16-3.46.The total dis-placement is 1.9 Kin.The differential stess is about 60-90MPa.It was formed at medium temperature of 400-500℃ and a higher strain rate.