<p>Food security is a strategic issue of global concern. In China’s major grain-producing regions (CMGPRs), conflicts among agricultural, construction, and ecological land are intensifying due to rapid urbanization and overlapping land-use demands, resulting in significant risks for food security. To address the lack of systematic analyses of spatial conflicts within the CMGPRs, in this study, a land-use suitability evaluation system was constructed for Heilongjiang, Jilin, Shandong, and Henan. The system analyzed the spatiotemporal evolution of land-use conflicts from 2005 to 2023, while employing the patch-generating land-use simulation (PLUS) model to project future land-use pattern under three scenarios: natural development, cropland protection, and ecological priority. The main findings can be explained as follows: (1) between 2005 and 2023, agricultural land suitability decreased by 10.23% in Northeast China (Heilongjiang, Jilin) but increased by 24.55% in Central China (Shandong, Henan), and construction land suitability improved across all four provinces; ecological land suitability decreased by 20.53% from 2005 to 2014 but increased by 34.62% from 2014 to 2023. (2) The “intensity of conflict between agricultural and construction land” increased significantly across the CMGPRs, with Henan experiencing the largest increase (24.86%). (3) Among all scenarios, the ecological priority scenario aligned the best with future sustainable development in the CMGPRs; by curbing construction land expansion and enhancing ecological space, this scenario contributed to increasing agricultural space, achieving synergistic benefits between agriculture and ecology. Overall, this study provides valuable practical insights for mitigating land-use conflicts in grain-producing regions, thereby promoting food security and sustainable development at the national scale.</p>