Aiming at the lack of on-line monitoring system of rice harvester's crushing rate, impurities rate and loss rate, this paper constructs an on-line monitoring system of rice harvester's operation quality. The GPS module in the system can realize the real-time monitoring of field operation speed and operation position. On-line detection devices are used to monitor the crushing rate, impurities rate and the loss rate during field operations. Each function module realizes data communication with a man-machine interaction system through CAN bus. A field experiment was carried out to verify the accuracy of the system. The results show that the accuracy of the on-line monitoring system for the rice harvester operation quality is 82.76% for crushing rate, 78.69% for impurities rate, and 73.53% for loss rate. In the field test, when the manual test results of operation quality increase, the system test results increase correspondingly, and when the manual test results decrease, the system test results decrease correspondingly. Therefore, the detection results of manual and system on the change trend of operation quality are consistent. Therefore, the on-line monitoring system of operation quality of rice harvester constructed in this paper can realize visual monitoring, give an alarm in time when the working quality of harvester becomes worse and provide powerful technical support for intelligent rice harvester and research on adaptive control strategy.