Abstract：Based on the field geological survey and the study of the measured profile of lacustrine sediments in Dingjie basin of Tibet, the authors conducted a detailed study and classification of the Quaternary lacustrine deposits distributed in the basin, redefined the middle Pleistocene–late Pleistocene stratigraphic units and established the sequence of biostratigraphy and lithostratigraphy. The authors have established for the first time the stratigraphic unit of Dingjie Group which belongs to middle Pleistocene–late Pleistocene lacustrine strata. Dingjie Group comprises middle Pleistocene Yeruzangbu Formation and upper Pleistocene Majia Formation. The lacustrine strata provide new material for the study of lake evolution, climate change, palaeogeographic change and division and correlation of Quaternary strata in the Tibetan Plateau.