NOVELTY - An artificial undercurrent wetland sewage treatment system which uses drop aeration to oxygenate, comprises one-stage or multi-stage drop aeration artificial undercurrent wetlands in series, in which each stage drop aeration artificial undercurrent wetland comprises bed body. A front end of the bed body has water inlet retaining wall. An overflow passage formed by the water inlet retaining wall and a bottom of the bed body is the water inlet. A tail end of the bed body has water outlet retaining wall.    USE - The artificial undercurrent wetland sewage treatment system is used for degrading pollutants in urban, town sanitary sewage, little industrial wastewater, and water from farmland. It is suitable for mountain area with certain grade and hilly area.    ADVANTAGE - The system has uniform water distribution, less dead water zone, and uniform water power impact. Retention time of the sewage in the bed body is prolonged without blockage and it helps improving biological degradation of water quality and microbe to nutritive materials (nitrogen and phosphorus) in the sewage. The system has low construction running cost.    DETAILED DESCRIPTION - Artificial undercurrent wetland sewage treatment system which uses drop aeration to oxygenate, comprises one-stage or multi-stage drop aeration artificial undercurrent wetlands in series, in which each stage drop aeration artificial undercurrent wetland comprises bed body. A front end of the bed body has water inlet retaining wall. An overflow passage formed by the water inlet retaining wall and a bottom of the bed body is the water inlet. A tail end of the bed body has water outlet retaining wall. A top end of the water outlet retaining wall is an inclined overflow dam for discharging water. Some guide plates, gravel filler, and emerging plant are in the bed body between the water inlet and water outlet retaining walls. The guide plates and bed body form the overflow passage, and the upper and lower overflow passages are arranged in a staggered manner. The guide plate on the most tail end and the bed body form the lower overflow passage. A water collecting region is formed between the guide plate on the most tail end and the water outlet retaining wall.