Abstract: Improving agricultural ecological efficiency is a crucial pathway to addressing the challenges of rural aging and achieving sustainable agricultural development. Based on panel data from 30 Chinese provinces during 2012-2023, this study applies panel fixed-effects, mediating effect, moderating effect, and threshold effect models to systematically examine the impact of rural aging on agricultural ecological efficiency and its underlying mechanisms. The results show that: 1) rural aging significantly reduces agricultural ecological efficiency, and this conclusion is supported by endogeneity tests and multiple robustness checks; 2) heterogeneity analysis indicates that the negative impact of aging is more pronounced in grain balance areas, low-aging groups, and high-education cohorts, while the effect in grain marketing areas is also significant, whereas the grain-producing areas show no significant influence; 3) mechanism analysis demonstrates that aging suppresses improvements in agricultural ecological efficiency by increasing carbon emissions, whereas technological progress can effectively mitigate this adverse effect; 4) further analysis reveals a nonlinear diminishing trend of the negative impact of rural aging as land scale expands. Based on these findings, this study proposes several policy recommendations: implementing differentiated agricultural development strategies, controlling agricultural carbon emissions at the source, strengthening green technological innovation and application, and promoting intensive land use and scaled operations to alleviate the adverse effects of aging on agricultural ecological efficiency.