Rural area of megacities is characterized by strong connection with the urban functions and the high diversification. The function evolution can be used to determine the function positioning for the multiple value and high-quality development of rural areas. Taking the rural areas in the periphery of Beijing as a typical case, this study aims to construct an evaluation index system of rural functional intensity suitable for the long-term sequence measurement, according to the connotation and classification of rural function. Then, Nelson classification was selected to measure and identify the functional intensity and functional structure in the different rural areas from 2000 to 2020. A summary was given on the evolution and formation path of the functional structure in the rural areas. The research results were as follows: 1) There were the significant regional differences in the functional intensity of rural areas in the periphery of megacities. Diversified forms were found in the functional combination. There was also the trend from the single-dominant dominant function to multi-dominant dominant function in the functional structure. The rural multi-function was evaluated as the basis for the classification of rural functional structure. The rural regional functional structure was represented by the differences in the path formation of rural regional functions. 2) According to the number and differentiation of dominant functions, the evolution of functional structure in the rural area on the edge of megacity was summarized into three development paths: "function strengthening and upgrading path", "function adjustment and transformation path" and " Functional comprehensive improvement path". Among them, there was the relatively simple functional structure of the exurb districts and counties far from the central urban area. The functional structure evolution was attributed to the functional strengthening and upgrading path. The path of functional adjustment and transformation was mainly taken, due to the instability of core functions. The functional comprehensive and perfect path was also taken as the optimization direction of the functional structure in the plain areas with the better development in the suburbs. 3) The agricultural safeguard function with the strength was the main initial function before the multiple transformation and differentiation of the functional structure of most rural areas on the edge of megacities. The life service function was strengthened in the primary measure, in order to promote the functional diversification and high-quality development of the rural area on the edge of megacity under the current urban-rural integration goal; 4) The evolution of dominant functions and functional structures showed that the development of different rural regions was defined to guide the formulation of their functional positioning, in order to promote the diversified functions and rural regional functional structure, as well as the determination of the development direction. The functional structure and the evolution path was introduced to determine the differentiated functional positioning. The typical regional cases were enriched the research perspective of the rural regional multi-function theory. The finding can provide the promising idea for the functional structure evolution and positioning in the development path decision-making of rural areas outside megacities.