The paleomagnitism dating of the core Co Ngoin, Qinghai-Tibetan Plateau, a 200-m-depth core taken from Co Ngoin, indicates that the lake emerges at 2.8Ma BP. Lithological property, grain size and magnetic susceptibility (sus) reveal three major significant environmental variations and at least two tectonic uplifts during the last 2.8Ma. Accordingly, pollen associations open out the vegetation changes controlled by the tectonic uplift. Studies show that the major environmental changes were largely controlled by stepwise uplift of the Qinghai-Tibetan Plateau, and those numerous small changes overlapped on the large tectonic background are mainly controlled by the global climatic changes of glacial and interglacial cycles in Quaternary. The thickness of the strata above the B/M boundary is thinner, which might be resulted from the glacial cover to lead the shortage in stratigraphic thickness.