In order to ensure the uniformity of seed delivery under the condition of high-speed operation of the air-suction seed metering device, the big-flat seeds with high proportion and big change in length, width and thickness in corn seeds were studied. The influence of seed adsorption attitude on seed delivery stability was verified through theoretical analysis. Considering the vibration caused by the uneven road surface during the operation of the seeder, the uneven seed delivery caused by the increased vibration was verified as disagreement. Using the method of DEM-CFD coupling simulation, the key factors affecting the seeding performance were analyzed, and it was found that the main adsorption attitude was lying flat at different rotating speeds of seed tray;the higher the proportion of lying flat seeds was, the higher the qualified index was, and the side lying seeds and vertical seeds jointly affected the multiple index and the missing index. It was found that the flat seeds at different rotation speeds were the main adsorption attitude, and with the increase of rotation speed, the proportion of lying flat seeds was increased gradually in the range of 1.6~3.6rad/s. The proportion of big-flat seeds in the side lying posture was increased slightly with the increase of rotation speed of seed plate, and then decreased rapidly to the lowest point of 5%, and then began to increase sharply, when the rotation speed was 4.1rad/s, accounting for 18%. With the increase of rotation speed, the proportion of oblate seeds in vertical position was firstly decreased and then increased, the highest point was 10%. In the study of the influence of seed adsorption attitude on seed performance, it was found that the higher the proportion of flat seeds was, the higher the qualified index was, the higher the proportion of side seeds was, and the number of multiple index was also increased. The increase of vertical seed proportion would have an impact on missing seeding. It can be seen from the analysis of seeding area that increasing the proportion of normal seeding, reducing the proportion of early seeding and delayed seeding can effectively improve the qualified index, and the different adsorption attitude can affect the timing of seeding, thus affecting the quality of seeding. The best seeding effect was in the area with an angle of 15°~30° with the horizontal position. Finally, wind pressure and rotation tests were carried out in the experiment of speed matching, the single factor tests of speed and wind pressure were carried out respectively, and the range of operation parameters was obtained. Then, the verification tests of speed and wind pressure were carried out. The results showed that increasing the proportion of seeds lying on the ground can effectively improve the seeding quality.