The Chuxiong Basin is a typical foreland basin formed in the Mesozoic. The Triassic is the main stage in the formation of the basin, and is an important age of a conversion from basin to mountain, and the transition period of sedimentary environment from marine facies to continental facies. At the same time, the Upper Triassic series is a significant source of oil and gas in the Basin. Based on a systemic study and analysis on the sedimentary, sequence stratigraphy, undulation geology and geochemistry of the Upper Triassic in the basin, three sequences are recognized, and sequence framework and high-frequency undulation curve of the Upper Triassic are reconstructed. The analysis of carbon and oxygen isotopes and trace elements reveals that the Chuxiong Basin had a marine environment during the late Norian to Rhaetian. The multi-disciplinary research results indicated that the Chuxiong Basin was a lake basin adjacent to sea in this period, and was affected by intermittent transgressions repeatedly. But the marine-facies hydrocarbon source rock and the continental-facies hydrocarbon source rock are different in hydrocarbon productivity and distribution. This understanding will have a vital significance in assessing the hydrocarbon source rock of the Chuxiong Basin.