The Qinghai-Xizang region with an elevation of 1000 m asl,was characterized by landscapes of the subtropical montane forest and forest-steppe in Pliocene.The intense uplifting of Qinghai-Xizang plateau.either the Himalayas in the south or the Kunlun in the north,began at the end of Pliocene and the beginning of Early Pleistocene.By a rough estimation,the accumulative uplifting of the Plateau has ammounted to 3500 m in elevation since Early Pleistocene,Three well-defined stages with alternating violent uplifts and relative stabilities are identified in the block faulted uplifting of the Plateau at the ends of pliocene,Early Pleistocene and Mid-Pleistocene,It may be manifested by three great knick points on the longitudinal profiles of rivers in the peripheries of the Plateau,