Abstract: An assembly line of rice seedling sowing can be used to effectively enhance the production efficiency with less labor intensity in the better adaptability of seedlings for machine transplantation. However, manual delivery has been confined to the large-scale operation of the number of trays in the front-end tray-splitting device. The current splitting tray device cannot fully meet the requirements of high-speed operations in conjunction with the rice seedling sowing assembly line. In this study, a mechanical pneumatic automatic splitting tray device was designed to rapidly and accurately split and supply trays, with a production efficiency of at least 2 000 trays/h. The high-speed sowing was suitable to equip with the 2BP-2000 rice seedling planter. Three mechanisms consisted of a splitting tray, a conveyor, and a limit auxiliary, together with a control system. The tray paddle was indirectly lifted or lowered by the extension and contraction of the cylinder piston rod, enabling continuous trays splitting of stacked trays. The maximum number of trays per stack was 10 trays. The structure and motion parameters of the tray splitting mechanism were determined during operation. The conveyor mechanism was divided into the tray and its splitting sections. The motion model of the seedling tray conveying mechanism was established using theoretical analysis. The conveying speed of tray tray-splitting section was about 2.5 times that of the sowing one under different production rates. The seedling trays were then conveyed without spacing. The control system was designed with PLC as the core, in order to determine the wiring logic and control flow. A single-factor test was conducted to clarify the effect of different production rates on the stability of the chuck and tray-splitting device. An evaluation index was taken as the splitting tray stability. The results showed that the better stability of splitting tray was achieved in not less than 98.67% at a production rate of 1 600 to 2 000 trays/h. A three-factor and three-level orthogonal rotary test was conducted to determine the optimal parameter combinations of the automatic tray-splitting device during tray-splitting. The test factors included the number of stacked trays, productivity, and tray quality, with the success rate of tray-splitting as the test index. There was the greatest influence of productivity on the success rate, followed by the number of stacked trays and tray quality. The success rate of receiving trays decreased with the increasing productivity. The success rate also decreased gradually with an increase in the number of stacked trays. The optimal combination of parameters was obtained with a productivity of 2 000 trays/h, a number of stacked trays of 6 trays/stack, and a tray quality of 750 g/tray. The average measured success rate of the tray device tray was 98.43%, with a predicted difference of only 0.29 percentage points. This disc device presented better adaptability to the trays of different weights. The structure and timing control system fully met the requirements of the application. This finding can provide a practical application value in the mechanization level of hard tray seedlings during rice sowing.