In order to improve the efficiency of vegetable grafting in large-scale planting，taking solanaceous vegetable plug seedlings as the object of operation, automatic grafting techniques and key mechanisms of vegetable grafting robot were studied. Based on the splitting method, the overall structure scheme of a grafting robot for synchronous grafting of six solanaceous vegetable seedlings was proposed. It can continuously realize the functions of automatic feeding of plug seedlings, cutting and plugging of rootstocks and scions, directional sequencing of grafting clips, and holding and clamping. The key mechanisms of the grafting machine, such as the horizontal cutting mechanism of rootstock, the splitting mechanism of rootstock, the pushing cutting mechanism of scion, the plugging mechanism of rootstock and scion, the vibration sorting and clamping device and the holding and clamping mechanism were designed, and the key structural parameters of each mechanism were determined. Taking pepper seedlings as the grafting object, orthogonal experiments on cutting quality of grafting robot was carried out. The results showed that improving the clamping accuracy and cutting speed of the seedlings, and reducing the fiber hardness of the stems were beneficial to improving the cutting quality. The cutting speed was set at 1.5m/s, and a prototype performance verification test was conducted on the grafted pepper seedlings. The results showed that the cutting qualification rate of the rootstock and scion was 98.6%, the grafting qualification rate was 97.1%, the grafting survival rate was 96.2%, and the grafting efficiency was 720 plants/h, which met the design requirements. This study provides support for the development of efficient multi-seedlings synchronous grafting robots.