Abstract: The facies of the Member l of the Qigu Formation (J₃q₁) in the central and western area of the Santai uplift of the south eastern Junggar Basin is still under debate, which constrains oil-gas exploration in the region to certain extent. In this article, methods of geology, seismic attributes, and seismic inversion are fully applied to define the facies. Data suggests that the Member l of the Qigu Formation (J₃q₁) is the products of a middle-distal alluvial fan, but not the facies of a braided river. The braided channel sandstone of the middle-distal fan is the main reservoir. The conclusion is helpful to map the distribution pattern and heterogeneity of the reservoir as well as the evaluation of the potential target. Favorable lithologic or fault-lithologic traps may occur in the proximal and distal parts of the fan system.