Abstract: The deformation belt of Southern Dabashan mountains, 1ocated between the northeast border of Sichuan craton of Yangtze plate and the Qinling collisional orogenic belt, is of a southward verging thin - skinned thrust wedge which is characterized by superimposition of dextral transpressive deformation. The thrust wedge is mainly composed of the stepped-thrust sheets, the fault-related folds and duplex in the cover strata. Kinetically, the propagation of stepped thrusts is in the piggy- back style from the root zone named the Chengkou- zhongbao thrust which is the northern boundary fault of southern Dabashan mountains where the largest depth of detachment layer is about 8- 10km to the frontal zone of Wenquanjing thrust which is the southern boundary fault of southern Dabashan mountains where the largest depth of detachment layer is less than 1.5km, at the end of Triassic, the thrust deformation was first initiated in the root zone near the Chengkou- zhongbao thrust. Since then the thrusting had propagated southwestward in the form of piggy-back and in the beginning of Cretaceous the deformation had extended to the southmost front of southern Dabashan mountains. Thus the total time span of deformation is about 50Ma. By mapping of balanced-cross sections and restoration of structures, the crustal shortening, the shortening rate and the thrusting velocity are estimated about 64km, 49.3 and 1.28mm/y respectively. Furthermore the geodynamics to develop the deformation belt is dominantly related to the Qinling collisional orogenic processes. In the Mesozoic, the continent- continent collision between North China plate and Yangtze plate resulted in the formation of Qinling collisional orogenic belt and the A-type subduction of Yangtze plate beneath the middle Qinling volcanic arc through the southern Qinling and northern Dabashan tectonic belts. As a result, the A- type subduction led to the horizontal tectonic stress which caused the southwestward propagation of the thrusting toward southern Dabashan mountain deformation bait. Besides, with the existence of Michang mountain uplifting Proterozoic metamorphic complex in the southwest of Dabashan mountains, the morphology of northern margin of Yangtze plate is in the form of northward convex. Under the controlling of this boundary condition, the northward A- type subduction deduced the dextral transpression to the east of Michang mountains uplifting Proterozoic metamorphic complex along the Chengkou-Zhongbao thrust and northern Dabashan mountains extruded eastward. It is this geodynamics that had caused the dextra1 transpression thin- skinned thrusting deformation in southern Dabashan mountains.