Abstract: Principles and methods of system science are applied in this paper to study the category, objectives, functions and structure of agricultural production system at county level, and "graphic model of agricultural production" is used to show the relationships among the factors within the system and that between the system and its environments. Then a mathematical model for agricultural production at county level is developed by using Linear Programming technique. Objective function in the model is to maximize the net return per capita, while the demands for the system by society, the limit to the resources within the system are considered as main constraints. After solving the model, analyse the obtained results and then sellect some optimized alternatives.