With the decomposition of the Langjiexue Group in recent years, it has been found that the previous studies on the Langjiexue Group, Nieru Group, Xiukang Group and Luolin Group are confused. The study of Langjiexue Group should be reconsidered. Moreover, it is controversial whether the above strata were formed in the same tectonic environments. In this paper, we study the heavy mineral characteristics, geochemical characteristics and paleontological fossils of the Langjiexue Group in the Jiedexiu Town, Langjiexue country, Gongga County, China. The chemical composition of major and trace elements in the Langjiexue Group are lower than the Clarke value of the crust. The average content of SiO2 is 74. 14%, and the average value of K2O/Na2O is 0. 70. The above characteristics indicate that the maturity of sandstone is low, and it has not undergone obvious epigenetic reworking. The chemical alteration index (CIA) is relatively concentrated, averaging 71. 55, which belongs to low- medium weathering degree, indicating that the climate and tectonic environment were in a relatively stable state. The average values of 100Mg/Al2O3 and CaO/Fe+CaO are 7. 85 and 0. 314 respectively, indicating that the Langjiexue Group formed in a deep- water anaerobic environment with moderate salinity and gradually deepened from north to south. Heavy minerals are mainly poorly separated zircon and rutile. ATi index is 93. 3~98. 97, ZTR index is 48. 01~85. 75, reflecting that volcanic rocks in the source area of the Langjiexue Group were abundant, and their transportation distance was relatively short. REE- La/Yb diagrams, Hf- La/Th diagrams, F1- F2 diagrams, Th/Sc- Zr/Sc diagrams and heavy mineral characteristics show that the source area of Longjiexue Group comprises intermediate- acid igneous rocks and continental margin clastic rocks. Based on the evidence of paleocurrent direction, the evolution of the Zhikong- Songdo Tethys Ocean, the Middle- Late Triassic magmatic rocks in South Gangdise, and the peak age (240 Ma) of clastic zircons from the Langjiexue Group, the provenance of the Langjiexue Group is South Gangdise. Tectonic discriminant diagrams show that the Langjiexue Group is a product of a specific tectonic setting between the continental island arc and the active continental margin environment, and the formation environment is closer to the active continental margin side. Paleontological fossils, represented by Halobia convexa, indicate that the Langjiexue Group was formed during the Carnian- Norian period of the Late Triassic. Based on the analysis of weathering degree, provenance area, tectonic background and formation age, the formation of the Langjiexue Group coincides with the evolution of the Yarlung Zangbo Tethys Ocean.