Abstract: The hydraulic system of combine harvester has a complex structure, and more driving components carry huge load changes. It is important to realize online monitoring of hydraulic drive unit of combine harvester to improve the efficiency of combine harvester. This study designs and optimizes the hardware configuration, software control system and fault alarm system of the combine harvester hydraulic monitoring system, which can collect and display the working parameters of the main working parts of the combine harvester in real time and send alarms to the user about the wrong working status. The results of field experiments show that the function and accuracy of the monitoring system fully meet the requirements of field operation, the accuracy rate of fault alarm is 96.5%, and the automatic diagnosis time of fault alarm is less than 1 minute and 18 seconds, which greatly improves the operation efficiency of combine harvester. The research results are useful for reducing the failure rate of field operation, greatly improving the operation efficiency and realizing the automation and intelligent development of combine harvester.