Establishing a reasonable assessment system for ecological environment vulnerability is very important to the high-quality development of ecological environments. This work collects Landsat 5/9 image， topography， soil， meteorological and socioeconomic data to assess ecological vulnerability by the CRITIC objective weighting method， then investigates spatiotemporal changes and its influence factors using transition matrix method and obstacle degree model in Tianshui city with a key position in water source conservation， soil and water conservation， and ecological security barriers. The result shows that the ecological vulnerability in Tianshui city presented a pattern of high in the north and low in the south， and generally decreased during 2000-2022. Except for Wushan and north-central part of Gangu with no change of extremely vulnerable areas， most area in Tianshui city had been transformed from extremely vulnerable areas to severely or moderately vulnerable areas. However， some areas surrounding the urban districts had been changed from moderately vulnerable areas to severely or extremely vulnerable areas due to urbanization. In 2022， bare soil， land use types， and precipitation are dominated factors for decreasing of extremely vulnerable areas. In order to effectively reduce the areas of extremely vulnerable areas in Tianshui city， the capabilities of planting tree and grass， artificial weather modification， and irrigation capacity should be improved continuously in line with the local conditions in future.