In order to improve the transfer efficiency of seedling tray in vegetable seedling raising line, and aiming at the problems of high labor intensity and low uniformity that exist in manual tray stacking, a multi-adaptive automatic tray stacking device for vegetable floating seedling was designed. The device was composed of frame, seedling tray conveying mechanism, tray stacking mechanism and the control system. The device took 200Smart PLC as the control core, and used the main and auxiliary conveyor belts to realize the transportation of the seedling trays, and combined the photoelectric sensor to realize the positioning of the seedling trays, which can complete the automatic stacking of foam seedling trays of different sizes, and the designed horizontal adjustment mechanism and vibration reduction mechanism can achieve the horizontal position adjustment of the seedling trays on the stacking mechanism and reduce the vibration impact of the stacking process. The test results showed that under the production rate of 450 plates/h of seedling line, the best effect of automatic stacking device was achieved when the wire diameter of the damping spring was 1.5mm, the speed gap between the main and auxiliary conveyor belts was 0.1m/s and the rising and falling speed of the electric cylinder was 0.13m/s for tray of 200 holes, and the success rate of tray stacking was 100%, and the deviation variance of tray stacking uniformity was 2.32mm2. At the same time, the amplitudes of X axis, Y axis and Z axis of the seedling trays did not exceed 0.8mm in the vibration detection test. And when 135 holes and 160 holes of foam seedling trays were replaced in the test, the success rate of stacking were 100%, and the deviation variance of tray stacking uniformity were 3.94mm2 and 5.98mm2, which showed that the device met the requirements of multi-adaptability. Under the optimal operating parameters, when the productivity of seedling line was increased to 900 plates/h, the maximum amplitude of the seedling trays was 0.709mm, and there was no significant change in the amplitude, which indicated that the device had good operational stability. The research results can provide reference for improving the stacking effect and reducing the vibration of the seedling line.