The fourth section of Xujiahe Formation in Fenggu structure of western Sichuan Depression is typical continental coal-bearing strata and widely develops the braided river delta. The authors analyze the evolution law of sedimentary microfacies in this paper. The results show that the fourth section of Xujiahe Formation experiences the complete process of transgression to regression. At the early stage and late stage of deposition, sand bodies are very thick and are mainly the splice and superimposition of multiphase underwater distributary channel. At the middle stage of deposition, sand bodies are relatively thin and mouth bar and residual underwater distributary channel develop and stably thick prodelta mud distributes among sand bodies.