3.8%。The dual-plates differential impact-based grain flow sensor of yield monitor systems was designed. The static force characteristics of sensor were experimental tested. Results indicated that the output signal of the grain flow sensor had nothing to do with the location of the point of application of the external force, and the linearity of the sensor could meet the application requirements. During the range of grain flow was 0~2kg/s, characteristic of the flow sensor was tested through laboratory and field. The sensor output voltage signal of the coefficient was gotten. Calibration coefficient K was determined through test. The error of grain flow sensor was 3.8% for rice harvester.