Abstract: In order to improve sowing qualified rate and stability of vibration-flow precision seeder, and reduce the effect of sowing qualified rate with the difference of seeds fluidity, a detection and control system of seed-layers thickness based on ultrasonic sensor was designed. With the system, seed-flow in the process of sowing was whole detected and automatic controlled. The results showed that the system could effectively detect the change of seed-layers thickness on the screening plate, and adjust the vibration amplitude and frequence of seeds-supply device based on different seeds fluidity to make sure that seed-layers thickness was kept in the setting range, and adjusting time was about 4.32 s after correction; When the difference of seeds fluidity was too large, alarm system was started; After the system was installed, sowing qualified rate of hybrid rice (2-5 grain per point) was improved from 80.1% to 87.3%. The research laid a foundation for further study of hybrid rice precision seeding apparatus.