Abstract: In recent years, the root knot nematode disease often occurred in Ding ji, Huainan, cultivation and management cucumber by most grafting black seed pumpkin in this region.The main symptoms of ill root hair after grafting was swelling, decay of the parts root, little or no lateral roots and fibrous roots.The light root was mainly some number root node of the parts root.In this paper, through root distortion (root knot or root nodes) percentage statistics, nodule number, root knot percentage method, 3kinds of method to compare the cucumber (grafted black seed pumpkin) root knot nematode disease index.The results showed that disease index of the nodule number and root knot percentage method are 25.33 and 42.67, root distortion (root knot or root nodes) to calculate disease index is 61.33, significant differences on the P0.05 compared with the number of nodule and root node percentage.Root distortion (root knot or root nodes) compared with the nodule number and root knot percentage method, the former can reflect objectively damage of different degrees.