Exploring the interplay between territorial spatial evolution and its ecological impacts on the Inner Mongolia Plateau from 2000 to 2020,focusing on spatial planning to strengthen ecological security,enhance agro-pastoral integration,and facilitate urban consolidation. Using transition matrices,the InVEST model,and multi-scale geographically weighted regression,this research delineates the ecological consequences of the "Three-Zone Space" transformation across urban,agricultural,and ecological sectors. Key insights reveal: (1) Urban expansion (0.50 million km²,+139.43%) alongside agricultural (-11.27 million km²,-18.26%) and ecological (11.27 million km²,+16.21%) zone expansion,with notable greening along the Greater Khingan Range and shifts from grasslands to grazing lands in the Xilin Gol Grassland. (2) An overall improvement in ESI (0.48,+55.57%) is observed,with higher indices in the southeast and lower in the northwest. Strategic zoning within main functional areas significantly influences these ecological outcomes,particularly in transitions from agricultural to ecological areas. (3) Natural factors,such as soil erosion and wind dynamics,promote positive ecological shifts,while socio-economic factors such as intensive grazing and tertiary industry expansion amplify negative effects in agro-pastoral zones. National policies provide a consistent regulatory framework. The study suggests optimizing urban spatial distribution,leveraging grassland resources within agro-pastoral layouts,and implementing a comprehensive ecological protection strategy to strengthen the crucial ecological security barrier.