Abstract: Aiming at the problem that the seed-airflow-mechanical multi-field coupling mechanism is not clear in the seed-metering device during high-speed operation of maize delta-row dense planting planter, as well as the seed movement law and airflow distribution characteristics are not clear, which affects the device's working performance. This study describes the overall structure and working principle of the air-pressure high-speed precision seed-metering device. Through theoretical analysis, simulation, bench testing, and field trials, the study investigates the influence of key working parameters on the performance of the device. Theoretical models for the seed-filling and seed-cleaning processes of the device were established. The DEM-CFD coupling simulation methods was used to simulate the working process of the device, explore the flow field characteristics of the device chamber and the shape holes, analyze the variation trend of the average drag force and velocity coefficient of variation of the qualified delta-row group seeds in the seed-cleaning zone at different seed-clearing angles, and reveal law of the motion of big-rounded, big-flat, small-rounded and small-flat seeds in the device. We defined the quality evaluation indicators for the delta-row sowing of the device, including qualified index of delta-row, qualified index of row-spacing, projection spacing qualifying coefficient of variation, row-spacing qualifying coefficient of variation. Full-factor bench tests were conducted with seed-clearing angle, chamber pressure, and operating speed as experimental factors, and high-speed sowing field experiments were conducted on maize delta-row dense planting in different tillage patterns. Simulation tests show that when the chamber pressure is in the range of 3.6～4.2kPa, the coefficient of variation of pressure is less than 2.9% and the coefficient of variation of flow velocity is less than 4.8%, which makes the distribution of flow field of the device more uniform and stable. By analyzing the seed-cleaning process, we obtained that in the range of seed seed-clearing angle of 3.0～4.0°, the average drag force of the seeds in the qualified delta-row group was higher than 0.06N, and the velocity coefficient of variation was lower than 5.29%, which made the seed-cleaning work more stable. By analyzing the motion characteristics of each type of seed, we obtained that the average drag force of the big-rounded seeds from the stable seed-filling to the seed-unloading point is 0.0793N, which is the more suitable seed type for sowing with this device. From the results of the bench test, under the conditions of seed-clearing angle of 3.0～4.0°, chamber pressure of 3.6～4.2kPa, and operation speed of 12～16km/h, the qualified index of delta-row of the device is not less than 70%, and the projection spacing qualifying coefficient of variation is not more than 12%. Field test results show that when the seed-clearing angle is 4°, the chamber pressure is 4.2kPa, and the operation speed is 12～16km/h, the qualified index of delta-row of the device is not less than 72%, the qualified index of row-spacing is not less than 85%, the projection spacing qualifying coefficient of variation is not more than 14%, and the row-spacing qualifying coefficient of variation is not more than 8% under different tillage patterns. The device can maintain high quality of delta-row sowing in both flat breaking and ridge plowing modes, and meet the requirements for precision sowing of maize. This study provides a basis for further improving the performance of the device.