Abstract: Impact-based grain mass senor possesses simple structure and can be applied easily，but it is sensitive to the base vibration caused by combine. So a load cell of parallel beam was developed with its installing side weakened, and corresponding FEA was carried out. Then results show that these measures are not only accordant with the rule of stress concentration, but also are able to improve the sensor power to resist the base vibration. The circuit of sensor was designed so that the standard current output could be obtained and the zero point of sensor could be adjusted easily. Finally, the experiment shows that linearity of sensor is within 0.1%, the output of sensor is independent of the change of acting point of external force.