The invention belongs to the environmental protection technical field, in particular to an eutrophication water body artificial wetland processing system taking steel-making waste residue as a substrate. The system adopts a horizontal subsurface flow artificial wetland mode and comprises an artificial wetland cell body, a substrate layer, a wetland botanical system and a water distribution system. The water distribution system comprises water distribution pipes, a gravel water distribution region, a gravel exhalant region and a water outlet channel. The substrate layer is arranged in the artificial wetland cell body. Two sides of the substrate layer are respectively the gravel water distribution region and the gravel exhalant region. The upper part of the substrate layer is paved with a covering layer. The surface of the covering layer is a wetland botanical system. One side of the gravel water distribution region is provided with the water distribution pipes. The gravel exhalant region is connected with the water outlet channel. The matrix material of the substrate layer adopts the mixture of steel slag and dry residue, the volume ratio of which is 4:4-6:1. The processing system is particularly suitable for the purification and restoration of water body with high turbidity, high N and P eutrophication in villages and small towns. Experiments prove that after contaminated cultivation and landscape water body is treated by the processing system; effluent quality basically meets the water standard of national surface water grade III, and even meets the water standard of national surface water grade II in some months; the removal rates of the TP and SS are both more than 90%; the removal rate of NH4<+>-N is also more than 80%.