Abstract: To solve the problems that the depositional environment of the Middle Permian Jingjingzigou formation in southern margin of Junggar basin is unclear and its sedimentary model is controversial, starting from 2 outcrop profiles such as Sigonghe and Sigonghe Coal Mine Plant, the paper makes a detailed study on the sedimentary characteristics of the formation, divides the formation into 11 lithofacies and 6 vertical sequences, identifies cyclic base levels including scour surface, lithofacies transition surface and flooding surface, concludes the abrupt change of paleoclimate from humid reducing environment to dry oxidation environment, and establishes a sedimentary model of braided-river delta for Jingjingzigou formation based on combination with typical profile analysis. The study shows that several sets of sandstones and mudstones deposited in the Jingjingzigou formation in the southern margin of Junggar basin, which are dominated by grey color and interbedded with several sets of coal beds. Large amount of debris of plant fossils can be noted in the formation, indicating a humid and warm paleoclimate which was suitable for vegetation growth. The interbedded red-brown sandstone in the middle indicates an abrupt change of the paleoclimate. Braided-river delta is mainly developed in the formation including distributary channel, swamp, interdistributary bay, underwater distributary channel and mouth bar etc. Relatively high sandstone ratio shows a characteristic of “mud coated by sand”. The base level rises continuously due to the influence of regional structures and downward half-cycle is poorly developed under the impact of river channel down-cutting