For the improvement of the water quality and eco-balance in the area of Jianghan hydropower station, the treatment of water-fall wetland to the combined sewer overflow pollution was investigated. The comparison with ordinary wetland illustrated the higher removal rates for COD, ammonia, total nitrogen, total phosphorous of the water-fall wetland, with the percentage of 13.1％, 7.9％, 6.1％ and 6.0％,respectively. The water-fall wetland embraced more appropriate gradient of dissolved oxygen, while the end of the ordinary wetland turned easily to be anaerobic. The Biolog Ecoplate confirmed the higher microbial utilization of carbohydrate and its derivatives, amino acids and its derivatives, fatty acid, lipid, metabolic intermediate and secondary metabolites in the water-fall wetland. PCR-DGGE analysis presented more diversified microbial structures in the water-fall wetland, and in which the dominant species were highly related with the removal of the pollutants.