Abstract: In this paper，we provide a high-resolution vertical distribution of Sr，Rb，Zr，Rb/Sr and Zr/Rb ratios in sediments from the lake of Co Ngoin．Central Tibetan Plateau．Combined with the lithological properties， grain size and clay mineralogy， we discuss the chemical weathering process recorded in lake sediments and reconstruct the history of the weathering intensity and paleoclimatic change in the last 2.8 Ma．The sedimentary records indicate that this region experienced three environmental evolution stages：in the core depth of 197～ 170 m (about 2.8～2.5 Ma)，the lower Sr content，higher Rb/Sr and Zr/Rb ratios indicate a strong tectonic uplift movement with a weaker intensity of chemical weathering；in the core depth of 170- 38.5m (between 2.5 and 0.8 Ma)，the higher Sr content，lower Rb/Sr and Zr/Rb ratios reflect a tectonically relatively stable epoch，with a warm ／cool and wet plateau climate；in the depth of 38.5～O m (about 0.8～O Ma)，the relatively lower Sr content，higher Rb/Sr and Zr/Rb ratios record relatively lower intensity of chemical weathering，caused by a cold climatic period．The plateau was uplifted to above 4 000 m above sea-leve1．