A real-time precision monitoring system for precision seeder was developed, and a single-chip microcomputer was used to process the signal of seeds dropping obtained by a photoelectric sensor. The information of seeds quantity, missing rate and multiples rate was all recorded in this system. A linear laser and patched photosensitive diodes which were arranged tightly in line were used as the emitter and receiver to achieve a no blind spot monitoring, it is better to monitoring seeds with an effective diameter of about 2mm or larger. A self-cleaning device was designed thereby guaranteed reliable operation of the monitoring system in severe environment. A pneumatic corn seeder and corn seeds “Nongda 86” were used in the experiment, meanwhile, a highspeed line camera was used to verify the accuracy of the system. Results indicated that the monitoring system had an accuracy of 98% in seeding quantity, an accuracy of 96% in missing detecting and a high reliability.