The invention provides a watermelon grafting method, comprising the steps of: first removing growing points and true leaves of a rootstock seedling, vertically downwardly cutting the center of a hypocotyl between two cotyledons by a blade to form a cut; cutting a hypocotyls below a cotyledonary node of a scion watermelon seedling to form a crescent-shaped cut; obliquely laying the watermelon seedling cut to the rootstock seedling cut to enable the crescent-shaped cut to fit one cut of the rootstock seedling, and conducting fixing by a grafting clamp. According to the invention, the root systemof the scion seedling is firstly kept during grafting, and the cut is close to a growing point, so that the survival rate is high; meanwhile, the grafting cut is relatively high and is not easily incontact with and contaminated by soil, thereby facilitating disease-prevention effect of grafting cultivation; and the method is easy to master compared with an inarching method, and the grafting efficiency is improved.