Abstract: The study aims to reveal the dynamic changes of agroecosystem and the unique man-earth relationship in agricultural production, and provides an effective theoretical basis for the sustainable development of regional agro-ecosystem, select a typical county-Yonghe County as a research case. [Methods] It was quantitative analysis of input and output of agricultural ecosystems in Yonghe County from 2000 to 2015 by emergy theory, and the sustainable development ability was comprehensively studied. [Results]The results show that: (1) The emergy input-output structure of Yonghe County''s agro-ecosystem is optimized continuously, and the agricultural production efficiency is gradually improved, but the system has strong dependence on natural environment resources but insufficient use, because of the insufficient economicemergy input , the development of agriculture was restricted.(2) From the perspective of emergy input, the renewable emergy of environmental resources has made a great contribution to agricultural production. The inputs of renewable organic emergy is gradually reduced and the inputs of non-renewable industrial supplemental emergy is increasing gradually. (3) From the perspective of emergy output, its output increased significantly, planting, forestry, animal husbandry tend to synergistic development, highlight the advantages of industry. [Conclusion] During the 16 years, the agricultural ecosystem function of Yonghe County has developed，the sustainable development ability was in a lower degree (average index 1.03), but notstable.