Abstract: The black rock series of Wufeng Formation and Longmaxi Formation are widely deposited from Late Ordovician to Early Silurian in the western margin of the upper Yangtze region. However, systematic studies on their sedimentology and tectonic background are scarce. In-depth studies on the geochemistry of samples from Wufeng Formation and the lower part of Longmaxi Formation in the Jinkecun section of Junlian County, Sichuan Province were conducted. Results show that the average σ ΣREE of Wufeng Formation in the section is 145.37×10⁻⁶, and that of the lower part of Longmaxi Formation is 158.54×10⁻⁶. Both are characterized by the relative enrichment of light rare earth elements and the loss of heavy rare earth elements. The enrichment of large-ion lithophile elements such as Rb, Th and U, and the loss of high-field strength elements such as Nb, Sr and Ti. Ce and Eu show weak negative anomalies. During the deposition period of Wufeng Formation, the water body first deepened and then shallowed, resulting in redox changes from hypoxic to anaerobic, and then to hypoxic condition again. When it entered the deposition period of Longmaxi Formation, the climate quickly warmed up, and the water body deepened and turned into a hypoxic environment again. The sedimentary characteristics of first accelerating and then slowing down from bottom to top and its relatively complex provenance of the Wufeng Formation reflect that the Wufeng Stage of the Late Ordovician was in an island arc environment during the arc-continent collision stage of the Yangtze Plate subduction and collision with Cathaysia Plate. It turned into a stable tectonic environment in the Longmaxi period. The single provenance also indicates that the Guangxi Movement in this area has ended in stages.