The impact-based grain flow sensor is widely used in the combine harvester yield monitor systems to measure the crop yield .but its accuracy wrecked by false signal of excessive natural vibration. A step response experiment was carried to identify the math function of the sensor. Experiment found that the math function of the sensor was a second-order vibration system, its Damping Ratio was 0.037, and its natural frequency was 125Hz, the overshoot reached 20%.To reduce the effect of the overshoot and natural vibration signal on the measurement accuracy, a dynamic compensation algorithm was designed with the series correction method. Step response experiment showed that the overshoot of the compensated sensor was reduced from 20% to 2%.