The aridification in the Asian Interior is one of the key climate events in the Cenozoic. Over the past score years, although numerous studies from separated locations within the continental interior obtain the fundamental framework for the aridification,discrepancy exists among various records from different areas,and the history of the aridification is still open to debate. To better constrain the evolution of aridification in inner Asia, a promising approach is to reconstruct a long-term, well-dated environmental history based on regional integrated analysis. In addition, Northwestern China is located in the internal arid area of Asian,with a typical continental climate,so the vegetation change in this region is more sensitive to the aridity. In order to achieve reliable vegetation change data, our collected palynological records are selected based on the following criteria: 1) the record should be well dated. The records constrained solely on lithological correlations or pollenchronologies are removed from consideration, and the remaining records are dated mainly by detailed magnetostratigraphic ages; 2) palynological records must cover detailed pollen spectrum information to ensure the accuracy of the biomization. A total of 30 palynological sequences met these criteria and have been used within this study. Then the chronologies of the palynological sequences were unified to the 2012 Geomagnetic Polarity Time Scale. Finally, we used the biomization method to reconstruct the vegetation changes in Northwestern China during the Late Cenozoic. The results show a relatively humid climatic condition with mainly forest in Northwestern China from ca.36Ma to 28Ma. Steppe started to expand during ca.27Ma and 24Ma, indicating an aridification trend, and changed to desert during the interval from ca.23Ma to 18Ma. Aridity was significantly increased since ca.8Ma, as evidenced by the replacement of forests by steppe and deserts. We attribute the early stepwise aridification to the retreat of the Paratethys Sea and to the uplift of Tibetan Plateau,and the subsequent gradual aridification trends to the ongoing Late Cenozoic global cooling. The significant aridification since ca. 8Ma may be linked with the enhanced cooling in the northern high latitudes.