In order to clarify the depositional environment of the Upper Permian Wutonggou Formation, the Dalongkou section at the southern margin of the Junggar Basin was taken as an example, and the following understanding was obtained by analyzing the lithology, lithofacies types, lithofacies assemblages, and spatial spreading laws of anatomical section sands. Three types of eight gravel, sand, and mudstone phases capable of characterizing diagenetic sands in the Wutonggou Formation were summarized. Based on the lithofacies, four lithofacies assemblage types were further established, representing the point bar, the cross-bank breakout fan, and the fluvial sands, respectively. Through the analysis of the lithofacies combination of the section, the sedimentary subfacies of point bar, crevasse splay, and floodplain in the period of Wutonggou Formation can be further identified, and the sedimentary response model of meandering river with the change of lake level was established. The sedimentary facies and sand body distribution of underground reservoirs were clarified by the results of outcrop research.