99.5%。A variable rate precision irrigating hill-seeder was designed, which could change the amount of irrigating water automatically according to the soil moisture content of the field. A control system integrating single-chip computer, global positioning system (GPS), geographic information system (GIS) and variable rate application (VRA) technologies was developed. The system employed a high speed single-chip W78E58 unit as the control center, a high capacity U-disk for GIS data transfer, and a self-developed GPS receiver as the locating device. The system could detect a falling seed through a photoelectric sensor installed insider the collector of the seeder, and then opened an electromagnetic valve to control water delivery so that the seed and water could fall at the same time and place. The amount of water was determined by the minimum soil moisture content required for seed germination. The control system was adapted to a maize hill seeder. A static calibration experiment showed that the controller had good linearity. The detection rate of the photoelectric sensor for the maize seeds reached 99.5%, which indicated that the control system had high control accuracy.