The Erlangping Group is bounded by the Waqiao ductile shear zone on the north and Zhuxia ductile shear zone on the south in the North Qinling tectonic belt. These two shear zones play very important role in the evolution of the Erlangping back-arc basin. This paper presents a detailed study on the two shear zones by geometric analysis,kinematic analysis and 40Ar-39Ar dating. The geometry and kinematics suggests that the Waqiao shear zone thrust from north to south,while the kinematic characteristic of the Zhuxia shear zone is thrusting from south to north in early stage,then dextral strike-slip in the Late stage. 40Ar-39Ar chronological study was undertaken on muscovite in the mylonite from the Waqiao shear zone and Zhuxia shear zone in this work. A plateau age of 387±1.7 Ma obtained from mylonite is interpreted as the deformation age related to the thrusting movement of the Waqiao shear zone. The geologic age of early thrusting activity of the Zhuxia shear zone was occurred in the late Paleozoic,and the later dextral strike-slip movement yield a 40Ar-39Ar plateau age of 146±2.8 Ma. Based on deformation characteristics and chronological data of the two shear zones,combined with previous geological data,the Erlangping back-arc basin is considered to be characterized by bidirectional subduction along the Waqiao shear zone and Zhuxia shear zone,respectively.