The existing image processing systems were always designed for certain items. One system can not deal with different types of items. In order to solve this problem, a designed method of parametric agricultural image processing system was proposed. Different parameters were set according to the different characteristics of items at first, and then different algorithms were chosen. The design and simulation results of the top-level controller of the system were presented. At last, the description of how to set parameters in the system was also provided. The system has strong flexibility and robustness.