According to the operation flow of cleavage-plug method for nutritional bowl eggplant seedlings, the mechanical system of the grafting robot was designed. The mechanical system includes stock operation part, scion operation part and public operation part. The stock operation part and scion operation part are introduced in detail. And simulation experiments are also done to test the validity of the mechanical system. Experiments show the developed grafting robot realizes automatic grafting of eggplant seedlings.