Abstract: The agro-ecological structure in the loess hilly regions was studied. with the data collectea in Guyuan County, Ningxia Province from the viewpoint of ecological integrity as well as conversions of materials and energy by means of systems analysis. A model of optimum eco-economic structure was developed. It can be seen from the calculation with this model that the natural resources will be fully exploited without disbalancing the ecological structure and the soil loss will be reduced by 50--80%. At the same time, the revenue of the system may be raised to about 2–5 times.