The invention discloses a reinforced soil composite structure drainage ditch. Reinforced soil composite structure bottom layers, reinforced soil composite structure middle layers and reinforced soil composite structure upper layers are arranged on ditch walls on the two sides of a drainage ditch from the bottom up sequentially, wherein capping layers are arranged on the top surfaces of the upper layers; a ditch bottom original soil layer is arranged in the middle of a ditch bottom in a length direction of the drainage ditch; water-permeable bottom angle protection layers are arranged on the two sides of the ditch bottom original soil layer respectively; macadam and coarse sand layers are arranged on the outer sides of the bottom layers, the middle layers and the upper layers and at the bottoms of the bottom layers; clay layers are arranged beside the macadam and coarse sand layers; and the external surfaces of the bottom, the top, and the inner side of each bottom layer are coated with geotextile. The drainage ditch is high in stability, and the permeability of the ditch walls is high, so that the drainage ditch effectively solves the technical problems that the interior of a ditch body of the field drainage ditch is completely isolated from soil outside, water in the middle layer and the lower layer of the field soil cannot be drained, the soil is waterlogged for a long term, the soil aeration and the water permeability become poor, the water in the ditch body in a dry season cannot re-infiltrate into the field soil, and a water resource is wasted.