In order to improve the field working performance, a kind of monitoring device for cleaning loss of combine harvester was proposed which primarily consisted of a monitoring sensor, signal conditioning circuit and an indicator. The results showed that the monitoring method and device for cleaning loss of combine harvester performed well. When the forward speed was 0.8 m/s, the error was 3.57%. Through the application of device during field work, the operator was informed of real time cleaning loss by using indicator light and alarm.