Features of the Upper Triassic flysch Langjiexue Group and Nieru Formation in southern Tibet were summarized and analysed by combination of the former and present works, within which stratigraphic property, fossil association, detritus component, sedimentation, geochemistry and metamorphism as well as deformation were contrasted. Study results show that most of the features are pretty similar between Langjiexue Group and Nieru Formation except for a few indexes such as subfacies, thickness, ratio of sandstone / slate, ZTR tendency. The discrepancy of the four indexes between is not suggested as real reasons to separate the two lithostratigraphic units because changes of subfacies, thickness, and ratio of lithology are normal within and among formations. The high similarities of features indicate that they could have been deposited in a same sedimentary basin and tectonic setting, probably in the basin related to orogenism. In another word, they could be formed in neither the passive margin (Himalayan terrane) nor accretionary wedge (Yarlung Zangbo suture). It is proposed that the Nieru Formation is a unit of the Langjiexue Group but not independent. Further more, the Renbu-Zhangda-Longzi fault is suggested as either the main fault of the Late Cretaceous oceanic subduction within the Yarlung Zangbo suture zone or a southern boundary fault of the Late Jurassic-Early Cretaceous subduction of the paleo-ophiolite crust.