Abstract: In order to achieve real-time measurement of operating area of farmland, the operating area measurement system of grain combine harvester was developed based on the ARM7 and the GPS. The hardware structures, including the memory, COM port and GPS access circuit were optimized. The corresponding driver was programmed with the C language. The experiment results showed that the real-time measuring system could record information including operating time, workplace, operating area and cost. At the same time, the system was not only suitable to measure areas with regular figures, but also had higher measurement accuracy for the irregular areas. The average measurement precision was 95.2%. The system provides the basis for measurement of the operating field area.