By comparing the states of energy flow in agricultural eco-systems before and after adjusting the agricultural, forest, animal husbandry ratios, the comprehensive harness which takes the optimizing structure as the central task and lay stress on the putting matrial and energy into the eco-system were regarded as the effective steps to turn the agricultural eco-system from a vicious circle to a fine circle, and were also regarded as a main measure to solve the agricultural production problem in Loess Hilly Area.