The invention discloses an under-ground soil-up ditcher in a root cutting ditch, belongs to the technical field of agriculture machinery and is used in machinery for seeding and fertilizing goat grassland after the root cutting. Different from the ground surface ditching theory of the conventional ditcher, the under-ground soil-up ditcher utilizes the narrow slits generated when cutting the roots, soil on two sides of the root cutting slits is extruded into the root cutting ditches through a soil-up wing (9) which stretches into the slits, and furthermore, under the cooperation of a main body stem (4), the soil extruded into the cut root is compacted to appointed depths so as to form flat ditch bottoms, then seedbeds and fertilizer beds are provided for seeding and fertilization. The under-ground soil-up ditcher adopts the theory that the soil is taken and turned up from the ditch bottoms to form the ditches, so that on one hand, the disturbance to the soil surface is greatly reduced, and the grassland environment is protected to the maximum extent, and on the other hand, the ditching depth is precise and identical, and the ditch bottoms are flat, so that the fertilizer efficiency can be brought into play and seed germination is facilitated; and moreover no new ditches are formed, so that labor is saved, and the energy consumption is reduced.