A symmetrical structure automatic grafting robot for Solanaceae vegetables was designed according to the grafting process requirements of Solanaceae vegetables. Under the control of a PLC system, it can continuously and automatically achieve functions such as picking, conveying, cutting, docking of rootstock and scion seedlings, as well as cutting, clamping and fixing the grafting clamp. The key structural parameters and control process algorithms of each mechanism were determined, with a focus on designing the seedling picking and delivery mechanical arm, seedling clamping mechanical arm, rootstock cutting device, cutting and clamping device, and control system that make up the grafting robot. Pepper seedlings were selected as the grafting object and the performance tests on the prototype of an automatic vegetable grafting robot were carried out. The experimental results showed that the faster the execution speed was, the lower the grafting qualification rate was. The degree of influence, in descending order, was the docking time, clamping time, and seedling picking time. The main impact of grafting seedling damage rate was concentrated in the process of picking, delivering, and cutting seedlings. The faster the execution speed of this process was, the higher the grafting seedling damage rate would be. On the basis of optimizing the execution time of each link, single factor structural optimization experiments were conducted on the height of the main gripper finger and the inclination angle of the cutting edge in the rootstock cutting device, and the optimal parameters for the height of the main gripper finger and the inclination angle of the cutting edge were obtained as 13 mm and 25°, respectively. The grafting efficiency of the optimized single plant vegetable automatic grafting machine was 300 plants/h, with damage rate of 2.5% and grafting qualification rate of 94.8%，which met the design requirements.