Sedimentary discontinuities exist between almost all of the Triassic and Jurassic stratas in the South Qiangtang Depression. The research on the stratas in this period has great significance to the sedimentary environment and its evolution. In this paper, the sedimentary environment and evolution characteristics of the study area are discussed by the analysis of the geochemical elements of the carbonate rocks of Upper Triassic—Lower Jurassic. Methods: The sedimentary environment of the rock was analyzed by the ratio value of V/Cr, Ni/Co, Sr/Ba, 1000×Sr/Ca, Sr/Cu et al. The source of REEs was analyzed by using the correlation between ∑REE and the content of Al2O3, Ti, Zr, CaO, Na2O and Sr; the tectonic background of the provenance area were analyzed by using La—Th—Sc and Th—Sc—Zr/10 diagrams; the source of carbonate terrigenous clastic material were analyzed by using chondrite standardized pattern map of REE and ∑REE —La/Yb diagrams. Results: Through the elemental analysis of Sobucha carbonate rocks in the Upper Triassic—Lower Jurassic. After removing the influence of terrestrial components, the V/Cr value is distributed in 0. 04~0. 47, the Ni/Co value is distributed in 0. 16~5. 38, the Sr/Ba value is distributed in 101. 33~277. 45, and the 1000×Sr/Ca value is distributed in 1. 30~1. 82, the Sr/Cu averate value is more than 10. The ∑REEs have positive correlation with Al2O3, Ti and Zr, but have no correlation with CaO, Na2O and Sr. The Ce and δCe have positive correlation with Al, the correlation coefficients are 0. 98 and 0. 77 but have no correlation with Ca. The Eu also have positive correlation with Al, K, the correlation coefficients are 0. 93 and 0. 88. Conclusion: The Suobucha carbonate rocks were deposited in an oxidative environment, the paleo- salinity of the sedimentary water gradually increased, and the paleo- water depth also gradually increased. Rare earth elements are mainly derived from feldspar- bearing terrigenous clastic components. The Ce negative anomaly is related to the oxidative environment during the deposition of terrigenous clastic source rocks, and the Eu positive anomaly may be caused by the weathering and leaching of feldspar- bearing source rocks. The La—Th—Sc and Th—Sc—Zr/10 diagrams show that the terrigenous detrital components have the tectonic setting of continental island arcs. The chondrite normalized model of REE and the ∑REE—La/Yb diagrams show that the terrigenous detrital components were mainly from the same sedimentary rocks. Combining the tectonic evolution and regional stratigraphic characteristics of the Qiangtang Basin, it is inferred that the source area of terrigenous clasts in the carbonate rocks is the Upper Triassic Tumengla Formation near the Central Uplift Belt, and the continental island arc structural background characteristics of terrigenous clasts are inherited in the clastic rocks of the Tumengla Formation. The Sobucha carbonate rock should be a sign of the expansion of the Bangong Lake—Nujiang ocean basin, and its formation indicates that the South Qiangtang Depression has entered the evolutionary stage of passive continental margin deposition.