In order to acquire field information in precision agriculture, a new measurement method of grain yield distribution is suggested based on weighing device. The new method could increase the accuracy of grain flow monitoring. According to grain transmission characteristics of the traditional combine harvesters, a new kind of grain flow sensor is developed with spiral propulsion weighing device. The device solves the several problems in present measurement system of grain flow such as direct power transmitting and effective signal detecting. Together with GPS positioning information, dynamic measurement of yield distribution information for grain combine harvester is realized.