The disadvantages of artificial grafting are low efficiency and nonstandard quality of grafted seedlings. Therefore, this method cannot meet the needs of mass production of factory seedlings. Mechanical grafting can improve the quality of grafted seedlings and promote the standardization of grafting seedlings. At present, most of the grafting machines adopt the artificial method to carry on the seedling, and the single hand grafting limits the improvement of the production efficiency. Through the development of automatic seedling device to replace artificial seedling, the device has high requirements for seedling standardization, the success rate of seedling is only about 80%, and it cannot be used in actual production. Through the study of multi claw synchronous grafting process flow and reasonable optimization of grafting mechanism layout, grafting efficiency can be improved steadily. In the process of mechanical grafting, the clamping and conveying mechanism is the key part of seedling transportation, which is used to grasp and transport seedlings from the seedling loading station to the cutting and docking station. In view of the existing single gripper clamping and handling mechanism, it needs to rotate back and forth at the seedling loading, cutting and docking positions during operation, which limits the grafting production efficiency of the machine, and there are some problems such as clamping injured seedlings, too long waiting time for operators to load seedlings, and easy to fatigue. A four gripper flexible clamping and conveying mechanism was designed. This mechanism can realize synchronous operation of seedling loading, cutting and docking, and realize flexible clamping and rapid transportation of seedlings. It was helpful to improve the grafting efficiency of the machine. The transfer mechanism can complete one grafting seedling every 90° rotation. At the same time, the flexible gripper based on buffer material and the adjustment method of clamping force were also proposed. The compression mechanical properties of EVA cushion material with different thickness were analyzed, and the clamping force of EVA cushion on different seedlings under the condition of completely closed clamping was obtained. By using ADAMS software, the dynamic simulation model of clamping and conveying mechanism was constructed, and the variation rules of different clamping force and rotation displacement of seedlings were analyzed. It was concluded that when the clamping force was less than 0.4N, the seedlings were free from the bondage of the clamping hand. When the clamping force was greater than 3.5N, the seedling clamping and rotating operation was stable. Based on the experimental results of mechanism performance, taking cucurbita moschata and cucumber as the test objects, the average success rate of the flexible gripper was 98.5%, which was 4.5 percentage points higher than that of the arcshaped gripper, and the injury rate was reduced by 3.5 percentage points. The grafting speed of the mechanism was 1052 plants/h, which was 1.72 times of the production efficiency of the same type of single claw grafting machine. The grafting success rate was 96.67%, which greatly improved the production efficiency of grafting robot and met the needs of industrial grafting seedling production. The results can provide a technical reference for the design and optimization of the clamping and conveying mechanism of the highspeed grafting robot.