Abstract: Precision seeding technology is one of the important technologies to realize cost saving and efficiency increasing in large-scale production. Precision direct seeding of rice has gradually become the main research direction of rice light and simplified planting. The real-time sowing monitoring system has an important contribution to improve the sowing quality of direct seeding machine, and can provide important support for the research and development of sowing rate real-time adjustment, real-time reseeding and the seeding evaluation quality system of rice precision direct seeding machine. At present, the methods of seeding monitoring are photoelectric-based, image-based and capacitance-based. However, image processing technology requires special equipment with high cost, and cameras are easy to be interfered by external light. For the capacitance-based method, when multiple small seeds fall simultaneously, the monitoring performance is not accurate enough. In order to monitor the sowing rate of precision rice hill-drop drilling machine in real time, in this paper, the surface-type photoelectric sensor installed in the seeding tube is used as the main monitoring element to design the monitoring system of precision rice hill-drop drilling machine. According to the structure and working principle of seed metering device, the installation modes of photoelectric sensor and rotary encoder are determined. In this system, the seeds flow in the seeding tube is taken as the research object. When the rice seeds pass through the photoelectric sensor monitoring area, it will cause the change of infrared beam intensity, which will lead to the change of photoresist voltage. The pulse signal from the photoelectric sensor is used as the time sequence to capture the interruption source, and then the monitored time sequence of rice seeds flow is obtained. The time division node is obtained by the synchronous monitoring of the seed metering time series and the rotation speed of the seed metering device. Based on the two adjacent time dividing nodes, the detecting time window of the seeds number per hill is obtained, each time window corresponds to one hill. The pulse width time of the rice seeds output in the monitoring time window is analyzed to get the seeds number per hill. Compared and analyzed the manual statistical data with the monitoring system statistical data, the test results show that the rotation speed of the seed metering device has a great influence on the monitoring accuracy of the average seeds number per hill, the variation coefficient of the monitored value of the average seeds number per hill grows up with the increase of the rotation speed of the seed metering device. When the rotation speed of seed metering device is 25-65 r/min, the relative error of seeds number per hill is less than 7.99% for Nanjing 46 (short grain variety), the monitoring errors of the number of hills is less than 6.07%; the relative errors of seeds number per hill is less than 24.07% for Xiangyaxiangzhan (long grain variety), the monitoring errors of the number of hills is less than 5.66%. The test results show that sowing rate monitoring system is applicable to different varieties of seed and has good detection accuracy, which can provide reference for improving the operation quality of precision rice direct seeder.