Abstract: The Henggong Co Formation is Late Triassic molasse occurring on the southern Qiangtang block. It consists predominantly of light gray-purplish gray variegated conglomerate with small amount of gray fine-coarse sandstone and is generally a sequence of river bed-point bar deposits. The fossil plants Neocolamites carcinoides Harris, Neocalamites rugosus Sze and Neocalamites sp. Obtained from the intercalation of siltstone are Late Triassic in age. The establishment of the Henggong Formation improves the stratigraphic system of the Upper Triassic Xo Caka Group and the discovery of the unconformity between the Henggong Formation and its underlying strata provides direct evidence for the study of the timing of transformation of the southern Qiangtang block to the Qiangtang basin and the termination of the Indosinian movement and Paleo-Tethys in northern Tibet.