Abstract: Outcrop section, sandstone clastic composition, geochemistry and cathodoluminescence images are comprehensively studied so as to analyze the depositional setting and provenance of Triassic nappe in the south of Bailang County, Tibet. Through field geological survey, the authors found that the lithology is composed of black mudstone, gray quartz sandstone, feldspar-quartz sandstone and gray limestone. The depositional background displays a neritic-bathyal environment in the Lagangguiri passive continental margin basin. Clastic composition and geochemistry indicate that the provenance was mainly derived from the craton basin. Cathodoluminescence images prove possibility of metamorphic, igneous rock sources. It is thus concluded that the strata consist of Lower-Middle Triassic Lücun Formation and Upper Triassic Niru Formation, with the provenance derived from the southern Higher Himalaya basement complex rock belt.