Based on the study of sandstone observation, provenance analysis and grain size analysis, this paper has a new understanding of sedimentary facies types and sedimentary environment evolution of the Zongzhuo Formation in Rongbu area.Results:Grain size analysis indicates that the water transport power is weak and turbidity deposition exists in the sedimentary period. The microscopic characteristics, geochemical characteristics and zircon U- Pb ages of three different types of sandstones in the Zongzhuo Formation indicate that the provenance of the three types of sandstones is different. In this paper, three types of sedimentary facies are identified from the Zongzhuo Formation, namely shelf facies, continental slope facies and deep- sea basin facies, and they are classified in more detail.Conclusions: The Late Cretaceous new Tethys Ocean crust subducted northward, and the initial collision between the Indian and Asian continents occurred after the subduction. Combined with the structural background analysis, this paper supposes that this is the reason that the sedimentary environment in the study area changes from semi- deep- sea environment to deep- sea environment. Based on the analysis of the strata and sandstone sources of the Zongzhuo Formation in the study area, it is concluded that the Zongzhuo Formation was a passive continental margin deposit during the subduction stage of ocean crust. During the initial phase of the Indo—Asian land—continental collision, the passive continental margin of the Tethys Himalaya ceased to exist and completely transitioned into a foreland basin.