Under the background of rapid urbanization, agricultural development in Beijing has shrunk sharply and the marginalization of agriculture is becoming more and more obvious. Recently, Beijing puts forward the development model of reducing quantity and improving quality, to meet the needs of the people and improve the quality of the ecological environment. In this context, the regional function of agriculture should focus on the production of high-quality farm products, the ecological protection, the high-end leisure and entertainment supply and the popularization of agricultural science and technology, as well as the promotion of urban and rural integration, etc. By using the data of 184 streets and towns, the research calculates the regional function of agriculture in Beijing. Results show that the spatial differentiation of agricultural regional function in Beijing is closely related to the structure of urban spatial development, which is generally shown an increasing trend from the core area of urban-rural fringe to the extended area to the far suburbs, and the declining trend of agricultural regional function in the extended area of urban-rural fringe is significant, which makes the city gradually lose the constraints of spatial development. The basic functions of agricultural products supply, ecological protection and employment placement in the far suburbs are strong and industrial integration, new business type and other modern functions are at a low level. Therefore, there is still great room for improvement of agricultural regional functions. The result of basic regression and quantile regression shows that, the land factors are the key factors that affect the regional function of the agricultural region in Beijing, and the location factor determines the scale of the agricultural land and the house price factor obviously inhibit the agricultural regional function in areas with the lowest score by accelerating the circulation of agricultural land. The non-agricultural industry has the function of promoting and not squeezing the regional function of agriculture. In the future, Beijing should focus on the regional function of agriculture, protect the agricultural land and fully tap the new urban agricultural support space, promote the organic integration of the agriculture into the modern economic system of the city so as to stimulate the new potential of agriculture; and optimize the method for realizing the regional function of agriculture.