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Considering the problem that in the broad width and high speed planting operation, there is a lack of distributor device of air-assisted centralized metering device which can match the planter to realize the stable seeding for rapeseed and wheat, a prototype of dome shaped distributor device that could achieve 24 rows seeding was developed. The working principle of the dome shaped distributor device was elaborated. The equation of the dome shaped surface of the distributor device and the relationship among the key parameters were determined. The influence of the conveying airflow and the structure of the distributor device on the seed delivery velocity were analyzed. The influence of the sphere radius of dome shaped upper arc plate, length of diversion baffle, and height of guiding seed outlet was tested with the quadratic rotation orthogonal combination experiment by DEM-CFD gas and solid coupling simulation. The experiment results indicated that when the sphere radius of dome shaped upper arc plate was 245mm, the length of diversion baffle was 20mm, and the height of guiding seed outlet was 20.5mm, the uniformity variation coefficient of seeding quality was better. Under the optimal parameters combination, the secondary mixing of seeds and conveying airflow could be realized effectively in the dome shaped distributor device, and the uniformity variation coefficient of seeding quality of rapeseed and wheat was 4.96% and 3.82%, respectively. The intelligent test platform for planting machines was used to carry out the seeding performance verification test of dome shaped distributor device under the better parameter combination. The bench test results showed that when the rotating speed of seed feeding device of air-assisted centralized metering device was 20~50r/min, the uniformity variation coefficient of seeding quality of the rapeseed was less than 5%, the variation coefficient of single row seeding stability of rapeseed was lower than 5.3%, the uniformity variation coefficient of seeding quality of the wheat was less than 3.9%, the variation coefficient of single row seeding stability of wheat was lower than 4.9%, and the damage rate was no higher than 0.05%, which met the performance requirements of rapeseed and wheat seeding.