In order to simplify the structure of seeding monomer, improve the quality of planting, and meet the agricultural requirements of narrow row of soy closely planting on planter, a centralized precision seed-metering device was designed. The method of slipped seed absorbing and impacted seed cleaning of seed-metering device was expounded. Through the analysis of the movement of the seeds in filling area, the pressure range of seed metering device for seed sorption was determined. The speed of the drop seed relative to the drum and the number of the suction hole passing through were analyzed. The force analysis of the multi-degree-of-freedom seal structure was carried out to determine the structural parameters of the hinge joint of gas chamber. The high-speed camera technology was used to conduct experiment, repeated experiment of two factors was conducted in which the test indexes were qualified index, and the missing index, the multiple index and the experimental factors were air pressure and operating speed. The results of the experiment showed that when the air pressure of seed-metering device was increased from 3kPa to 4kPa and the operating speed was in the range of 4~12km/h, the qualified index showed a trend of declining with the increase of working speed. When the air pressure was increased from 5kPa to 7kPa and the operating speed was in the range of 4~12km/h, the qualified index showed a trend of declining after the growing with the increase of working speed. The missing index was in decline with the increase of pressure value and in rise with the increase of operating speed. The qualified index was more than 95% and the missing seeding index was less than 2%, while the air pressure was 5kPa and the operating speed was in the range of 4~12km/h. This seed-metering device could meet the seeding requirements well.