Abstract: The electronic monitor system of tractor was designed. 8031 microcontroller of MCS-51 series was used as its center. This system has four LED digit meters, nine indicative lights and eleven sensors. It has some intelligence, which can monitor a lot of places, show the difference between ordinary and urgent breakdowns and show the urgent breakdown first. The test result showed this system has the function of the advanced technology and reliable work. This system may provide the advanced technology monitor system for large wheel type tractors.