The Alxa block constitutes the westernmost part of the North China Block (NCB). This block has experienced polyphase tectonothermal events and hence serves as a key tectonic unit of the NCB. In this paper, Mesoproterozoic Nuoergong Group in Bayinnuoergong area of eastern Alxa block was selected for studying the tectonic framework and deformation stages of the Alxa block. Based on geometry, kinematics and microstructural characteristics of the Mesoproterozoic Nuoergong Group, the authors recognized two deformation stages. At the first stage, original bedding structure reflected by the ribbon was transformed into foliation, striking in the NE-SW direction. At the late stage, dextral strike-slip shear occurred along the strike of foliation. In combination with previous research results and geochronological data, the authors hold that the deformation structures were controlled by the subduction of Chaganchulu back-arc basin beneath the Alxa block during Carboniferous-Permian period. Due to the intense NW-SE-trending contraction during the subduction, foliation formed and transformed the original bedding structure. After that, dextral strike-slip shear occurred along the strike of the subduction zone and accommodated intense contraction.