Abstract: Whether there was exposure erosion of the Lower-Middle Ordovician top in Beiweixie region of the middle Tarim Basin, it is critical to identify the controlling factors for reservoir development and exploration direction in the study area. Through the analyses of the reflection characteristics of new 3d seismic profile, R_o thermal evolution profile of drilled well, and δ¹³C, δ¹⁸O isotopes of fracture-filling calcites, it is concluded that the Lower-Middle Ordovician top may have suffered various degrees of exposure erosion in Beiweixie region under the action of the episode Ⅰ of the mid-Caledonian. Denudation degree increases approaching to the Tazhong No. Ⅰ fault belt, which enhances the oil and gas exploration potential of weathering crust karst areas of the episodeⅠof the mid-Caledonian in the study area.