Clarifying the spatiotemporal development of regional ecological security can support decision-making related to coordinated, sustainable regional development. This study used an emergy ecological footprint (EEF) model to analyze spatiotemporal changes in ecological security in the Dingxi region, a fragile-environment area in western China. The results indicated that in all counties in Dingxi, the change trends in emergy ecological carrying capacity per capita (eec) were not significant while spatiotemporal differences in emergy ecological footprint per capita (eef) was significant. Overall, the eef in 2019 is 0.2–1.3 times higher than in 2001(except Minxian), respectively. Zhangxian had the highest eef (2.74 ha/cap), followed by An'ding (1.47 ha/cap), while Minxian was the lowest (0.50 ha/cap). During the study, Minxian recorded an ecological surplus, the ecological pressure index showed a decreasing trend, the ecological security level increased, and sustainable development ability was stronger than in the other counties. Other counties are in a state of ecological deficit and have a high ecological pressure index, and regional ecological security is facing great challenges. Moreover, industrial structure, economic level, urbanization, and population size are the main drivers of ecological security in the Dingxi region, while geographic location and climatic factors are the dominant factors leading to its spatial differences. Therefore, controlling population size, reducing the use of nonrenewable resources, developing land resources appropriately, and using resources efficiently can promote the sustainable development of counties. Our findings could serve as a reference for the ecological construction and economic development of the counties.