Research about coupling in agricultural ecological economic systems is important for the establishment of an efficient and sustainable agricultural production system. Knowledge about the degree of coupling can help clarify interaction between the agricultural and economic systems and be used to judge the state of the agricultural ecological economic system. In this paper, the author established a coupling factor model for the agricultural and economic system in the Zhifanggou watershed, Shaanxi Province. Analysis was conducted using data collected over 70 years. The results indicate that the coupling process in the agricultural ecological economic system can be divided four stages: I. A stage of primitive agricultural production in which which the economic system depends on the ecological resources; II. A stage in which agricultural production exploits ecological resources and the ability of the system to supply resources decreases unceasingly; III. A stage of coordinated development of the agricultural and economic systems; and IV. A stage in which the speed of agricultural development is reduced and reconstruction of the agricultural ecosystem is promoted. The agricultural ecological economic system passed through stages I, II, and III between 1938 and 2008. Currently the system in the Zhifanggou watershed is at stage III, however the process of system development has concealed the continued growth of a potential crisis. Analysis shows that system coupling will break through the coordinate boundary in 2018. This will result in the clear manifestation of conflict within the system. For this reason, it is important to re\|adjust the distribution of industry in the region, promote the development of pastoral animal production, and optimize the industrial structure in order to realize harmonious and healthy development within the agricultural ecological economic system.