In order to reveal the paleoclimate evolution of the Oligocene-Miocene sediments in the Gerze Basin, Tibet, the authors used X-Ray diffraction (XRD) to analyze the Mineral assemblage characteristics in combination with the sedimentary environments and sedimentary facies of Gerze Basin. The results show that the main minerals in the sediments are quartz, feldspar and calcite, with small amounts of dolomite, and their relative content varies along the section. Variations of relative values and ratios of quartz/feldspar suggest that the Gerze Basin has experienced four-stage paleoclimatic evolution: Stage I (early Oligocene), characterized by high quartz and carbonate mineral content and low feldspar content; dolomite occurred frequently at this stage, and the content changed significantly, indicative of a dominant seasonal arid climate; Stage Ⅱ (late Oligocene), characterized by high quartz content, which, however somewhat decreased, indicating a colder and drier climate; Stage Ⅲ (early Miocene), characterized by high quartz content; nevertheless, compared with features of the previous two stages, the quartz content further decreased, the content of feldspar further increased, and carbonate tended to become an overall increase. Compared with the previous two stages, dolomite increased significantly whereas quartz/feldspar ratios decreased, indicating that the climate became colder and drier; Stage Ⅳ(mid-Miocene), during which quartz content relatively increased, feldspar and carbonate minerals content decreased, quartz/feldspar ratios also increased ; nevertheless, compared with Stage I and Ⅱ , the quartz/feldspar ratios remained small, indicating that the climate was somewhat recovered, but still in a cold and dry environment. Compared with the uplift of the Tibetan Plateau and the global climate change, the authors hold that that climatic periodic changes during Oligocene-Miocene in the Gerze Basin might have been caused by plateau uplift and the global climate change.