Abstract: In order to improve the automation and intelligence standard of the seed processing equipment, a set of control system based on Micro Controller Unit(MCU) was proposed. The system is modular designed, and can be divided into the main control circuit based on C8051F020 as the core and the external control circuits. With these modules, certain control system can be built up easily by selecting modules with corresponding function. Furthermore, the real-time operating system μC/OSII was transplanted into the main control board. With its help, the coding of the controlling program has been simplified as the planning for all the tasks, which would be also helpful for improving the reliability and shortening the development time. The whole system has successfully been applied into the control of the seed drying machine. The result indicated that the system can easily fulfill the aim to create a common controlling system with a low cost.