In recent decades, escalating climate change, continuous population growth, rapid urbanization, and extensive agricultural development have placed increasing pressure on global ecosystems. Particularly in China, intensive agricultural practices and excessive water resource consumption have led to severe ecological challenges, threatening the health coupling of the food-water-ecosystem (FWE) function nexus. It is therefore critical to assess the impacts of multiple environmental changes on the FWE coupled system. Here, we employed an assessment process, 'indicator selection - element quantification - trade-off/synergistic effects - driving forces', to elucidate the intricate dynamics of the FWE nexus from the perspectives of climate change, socioeconomic development and ecological restoration in a typical ecologically fragile region (the agro-pastoral ecotone of northern China, APENC). The results indicate that between 2000 and 2020, crop production in APENC increased from 45.8 Mg/km2 to 140.7 Mg/km2, while water yield remained low but showed fluctuating growth. The expansion of forest land contributed to the regional soil carbon sequestration, with carbon storage (CS) increased by 10.0%. Soil conservation (SC) and habitat quality (HQ) also increased by 76.8% and 1.6%, respectively, contributing to the mitigation of soil erosion and habitat loss. Over time, trade-offs within the FWE nexus weakened, while synergistic effects grew stronger. Climate conditions were most strongly associated with the FWE nexus, with precipitation contributing approximately 29.4%-34.3%, while ecological restoration has partially mitigated cropland expansion in APENC, thereby improving the ecological environment. However, the negative pressures brought about by rapid socio-economic development should not be overlooked.