Abstract: Abstract: At present, dimension-positioning method is adopted as the main method for grasping tissue culture seedlings in tissue culture transplanting equipments. But the majority of gripper structure based on dimension-positioning is complex, which causes that the precision of the operation can not be improved. Meanwhile, young tissue culture seedlings will certain be damaged by the gripper in the process of clipping , which affects the survival rate of the transplanted tissue culture seedlings. To solve such problems, this study designed a force-positioning pickup system based on vacuum adsorption, which can transplant banding tissue culture seedlings. The pickup system for tissue culture seedlings mainly consists of three parts, including vacuum production part, negative pressure detection part and the suction nozzle part. The suction nozzle part is the key part, which decides the holding effect of tissue culture seedlings. The core of suction nozzle is inner soft tube made of silicone rubber with a metal shaping pipe sleeved outside. To increasing the adsorption area, the suction nozzle lip is shaped as oblong. In this paper, design and experiments are both mainly focused on the structure and parameter of suction nozzle. The process that suction nozzle picks up a tissue culture seedling can be divided into two phases: adsorption phase and holding phase. In adsorption phase, negative pressure flow field in the suction nozzle, which is generated by the vacuum generator, will help the seedling overcome its gravity, so that the seedling can be absorbed and adhered to the suction nozzle lip closely. In holding phase, the suction nozzle lip and the stem of tissue culture seedling joint closely, and a vacuum cavity emerges with less leakage in the suction nozzle, then the vacuum cavity generates the force for holding the tissue culture seedling. In adsorption phase, there are two schemes about negative pressure inner cavity of suction nozzle, and they are deformed cavity and parallel cavity. To get the average velocity of flow field near suction nozzle lip, simulation analysis have been carried out based on each of the two cavity with CFD (computational fluid dynamic) software in adsorption phase. The corresponding verification test also have been done, and the results supported that deformed cavity will be used in the pickup hand system because the suction nozzle using deformed cavity can produce flow field with higher velocity, and hold tissue culture seedling more steadily. In holding phase, a series of orthogonal experiment, single factor experiment and interaction experiment were carried out, to test the impact factor about tissue culture seedling holding strength, including thickness of suction nozzle tube, diameter of suction nozzle tube, radius of oblong suction nozzle lip and height of suction nozzle lip. The experiments results show that the optimum parameters for the tissue culture seedlings of suction nozzle are 0.5 mm thickness of suction nozzle tube, 6 mm diameter of suction nozzle tube, 0.7 mm radius of oblong suction nozzle lip and 1.5 mm height of oblong suction nozzle lip in experiments. With these optimum impact factors, suction nozzle can hold banding tissue culture seedlings steadily whose diameters range from 1.2 to 2 mm. It is noteworthy that overall success rate of negative pressure pickup system for banding tissue culture seedling can reach up to 98%, which successfully meets the requirements of insertion in next operation for transplantation.