The real-time assessment of ecological conditions in arid and semi-arid regions is essential for global ecological sustainability. This study utilizes an improved three-dimensional ecological footprint model to assess the ecological footprint, ecological carrying capacity, and footprint depth of Xilingol League, analyzing its spatiotemporal evolution characteristics. An ecological pressure index is developed to evaluate ecological security, and two-way ANOVA and M-K mutation tests are employed to analyze the effects of county-level and year-level factors on these indicators and their evolving trends. The results show that the following: (1) From 2011 to 2021, the ecological footprint and footprint depth in Xilingol League first increased and then decreased, while its ecological carrying capacity slightly improved, leading to an overall reduction in ecological deficit. Spatially, ecological footprint and carrying capacity were higher in the northeast than in the southwest, and ecological pressure was higher in the eastern and western regions compared to the central area. (2) Grassland ecological footprint and footprint depth were relatively high, with a higher carrying capacity than other land types; however, the ecological deficit was severe, reaching a minimum value of -5 in 2019. (3) County-level factors had a significant impact on ecological footprint, carrying capacity, ecological balance, footprint depth, and ecological pressure, while year-level factors significantly influenced footprint depth and ecological pressure. (4) From 2013 to 2021, the ecological footprint significantly increased, while ecological carrying capacity notably improved from 2016 to 2021; however, ecological balance remained in a deficit. Footprint depth showed a significant increase from 2011 to 2016 and a significant decrease from 2016 to 2021, while ecological pressure significantly increased from 2011 to 2018 and then significantly decreased from 2018 to 2021. This study highlights the spatiotemporal dynamics of the ecological system in Xilingol League and provides scientific support for ecological management in arid and semi-arid regions.