Abstract: Abstract: The key factor to improve seeds pick-up accuracy of vacuum plate seeder is to control the suction position accurately. During the working progress, the number of seeds in vibrating tray is always changing. So, it is an important guarantee for improving the continuous working performance of seeder that the suction position of vacuum plate can be adjusted automatically according to the variation of seeds in vibrating tray. In the paper, 2 different ellipsoid paddy seeds models were established using multi-sphere fitting method, and the contact forces were calculated using Hertz-Mindlin model. Then, the kinetics simulations of seeds pick-up process were completed using CFD-DEM (computational fluid dynamics- discrete element method) coupling method which includes the standard k-ε turbulence model and Euler gas-solid two-phase model. According to the spatial distribution variation law of seeds in vibrating tray at different time, their distribution region and discrete coefficients were calculated using the uniform distribution model and the moment estimate algorithm. Discrete motion states and stability characteristics of seeds under excitation of vertical reciprocating vibration were obtained, and the reasonable range of seeds layer thickness was determined. Seeds pick-up processes were finished when the seeds were thrown up to the high point by vibrating tray, and the absorbed seeds were generally in the upper layer. Under the conditions that seeds could be picked up accurately, the critical suction position in different seeds layer thickness was determined, and then the variation of pick-up distance, the influence of seeds shape on the pick-up performance, and the reasons leading to seeds single pick-up, missing pick-up and repeated pick-up were analyzed. It was obtained that the repeated pick-up ratio will increase with the increasing of seeds ellipticity which leads to the strong leakage flow field. Under the influence of collision and extrusion between seeds, the pick-up distance received by simulations is less than the value at static condition. Considering the influence of uncertain motion state of seeds in actual vibrating tray is much stronger, a modification method of suction position was proposed to improve the overall seeds pick-up performance of vacuum plate. That is to properly reduce the regulated distance based on the critical suction position received by simulation. Combined with the real-time monitoring method of seeds mass, an adaptive control device of suction position of vacuum plate was designed using PLC (programmable logic controller) as the controller. Using the established suction position control model, and taking differential pressure, regulated distance of suction position, vibration frequency of tray and seeds layer thickness as factors, each nozzle picking-up 1-2 seeds as evaluating indicator, the orthogonal tests were carried out on precision seeder test-rig with the diameter of suction nozzle of 2.5 mm and vibration amplitude of tray of 4 mm. The mathematical regression equation of seeds pick-up qualified index was established based on orthogonal tests results, and it was shown that the differential pressure and regulated distance of suction position were the 2 major factors that affected operating performance. By optimizing the established mathematical regression equation, the ideal working parameters were received including differential pressure of 4.4 kPa, vibration frequency of 10.6 Hz, and regulated distance of suction position of 2.7 mm. Under the above optimization parameters, further seeds pick-up tests were carried out with the seeds layer thickness varying in the range of 15-25 mm, and the results indicated that the seeds pick- up qualified index could reach about 94.5%. The proposed control method of suction position according to the variation of seeds layer thickness in vibrating tray can provide references for improving automation level and operating performance of vacuum plate precision seeder.