Aiming at the problems of small size, light weight and pityriasis in millet seed sowing and seed-metering device, such as hole blocking, poor seed uniformity and low seed filling rate at high rotating speed of seed-metering plate, a combined type of positive and negative air pressure and hole wheel seed sowing and seed-metering device was designed according to the agronomic requirements of millet seed sowing. The parameters of key parts of seed sorter were designed and calculated, and the mechanical model of seed in the flow field and filling area was established through theoretical analysis. It was found that the main factors affecting the airflow force on seeds were the diameter of suction hole and the vacuum degree inside the type hole. The vacuum degree required by seed sorter during seed filling was 1.13~3.21kPa. Through single factor test, it was determined that the optimal hole of the seed metering device was cylindrical conical composite hole, and the optimal hole diameter was 1mm, and it was verified that the pass rate of the hole metering device under the condition of negative pressure at high speed was significantly higher than that without negative pressure. In order to get the best performance parameters of the metering device, with hole type wheel speed, vacuum degree, and suction diameter as the test factors, percent of pass, replanting rate, sowing rate as the evaluation index, the three factors five levels quadratic orthogonal rotation combination test was taken, and multi-objective optimization method was used, and the best parameter combination was determined as follows: when the suction diameter was 1.04mm, the vacuum degree was 2.10kPa, hole type wheel speed was 22.46r/min, the percent of pass was 93.14%, the replanting rate was 3.48%, the leakage rate was 3.38%. The verification results were basically consistent with the optimized results. In order to investigate the actual sowing performance of seed metering device, field seeding experiments were carried out. The field test results showed that the pass rate was 88.2%, the replanting rate was 4.9%, and the leakage rate was 6.9%. All the indexes met the requirements of hill seeding agronomy of millet.