The invention belongs to the field of sewage treatment, and discloses a sewage purification system. The sewage purification system comprises a watercourse, wherein the watercourse is at least 1000 meters long, at least 3 meters wide and 1-4 meters deep. An emerging plant area, a water-planted commercial crop area and a submerged plant area are planted along the watercourse in the flow direction of the sewage, wherein the emerging plant can be cane shoot or lotus root; the water-planted commercial crop can be water-planted cress, leaf lettuce, lettuce, water convolvulus, ryegrass or the like in spring and summer, or water-planted green vegetable, shallot or the like in autumn and winter; the sunken plant can be waterweed, Potamogeton crispus L or eel grass; and at least 100kg of spiral shells and at least 100kg of freshwater mussels are stocked in the watercourse. By planting the emerging plant area, the water-planted commercial crop area and the submerged plant area in the watercourse of the sewage treatment system and simultaneously stocking the spiral shells and the freshwater mussel filter-feeding benthic species, the invention intensifies the wetland ecosystem restoration function, can effectively improve the water quality, is especially applicable to the purification of rural domestic sewage, and can be used as the matching technology for new countryside construction.