Abstract: Pollen fossils such as Classopollis, Annulispora, and Chasmatosporites as well as abundant dinoflagellates like Systematophora cf., and Ctenidodinium, which indicate Middle-Upper Jurassic strata with a typical significance, were found in the formerly-regarded Middle Permian Xiala Formation within the Tarezeng area, Tibet. The findings show that at least part of Middle-Upper Jurassic strata has not been identified previously in the Xiala Formation. The assemblage characteristics of the rock, basic sequence, and fossil comparison show that this set of strata belongs to the Ringtor Formation. The determination of this formation provides basic information for the correlation of regional strata, the establishment of the stratigraphic framework and the investigation of the evolution of the Mesozoic basin.