Terrestrial ecosystems function supply food (e.g. grains, vegetables), maintain diversity, and prevent environmental contamination. Thus, it is important to human well-being. Food production is vital for the sustainable development of human populations, and its dynamic spatiotemporal factors are closely related to spatial geographical heterogeneity and social development. However, there are only a few studies on the universal dynamic evaluation methods for ecosystem function used at the regional scale, especially in the fragile mountains of China. Bailong River Watershed (BRW) is located in the transitional ecotone along the Tibet Plateau, Loess Plateau and Qinba Mountains, and it was selected to analyze the spatiotemporal heterogeneity of ecosystem food production. Based on a field survey employing land use data, model simulations, and GIS spatial analysis, the ecological conditions and socio-economical factors were used to revise the previously held dogma which put forward by Costanza in 1997. Specifically, sources of hazards reflected the differences in ecological conditions. The resource scarcity theory and the willingness to pay were used to revise and calculate the economic developmental coefficient. A dynamic evaluation model was constructed with the above corrections method and applied for ecosystem food production services assessment in the Bailong river watershed during 1990-2010. In addition, spatiotemporal heterogeneity and food production were analyzed by ArcGIS 9.3. The results indicated that the supply of cropland distributed in the river valley and bank area of BRW, hill slopes, low mountain regions and decreased. The area of instable cropland and the index of social progress increased. In the period of 1990-2010, ecosystem food production value increased. The mean value of food production was 1.8674 million Yuan in 2010. In addition, the spatial distribution pattern change of food production value was not obvious. Land accounting for high yield of food production value was 42.4% of the total area, which was mainly distributed in the valleys of BRW between Zhouqu and Hanwang town, the northwestern part of Tanchang County. The low-yield areas of food production distributed in the national nature reserve and forest. Our data change how the value of China's terrestrial ecosystem was previously defined on a national to regional scale. Compared with a previous evaluation model, the change in food production was smaller using our method, and its spatial pattern was a better fit to the natural system of the Bailong river watershed. These data indicate that natural hazards (such as landslides and debris) and human activities affected food production and its value.