A layer effect study was conducted to investigate the transformation of nitrogenous pollutants in two batch subsurface horizontal constructed wetlands. Artificial drainage water containing a low concentration of chemical oxygen demand (COD_Cr), but high concentration of ammonia and nitrate, was treat in two batch wetland cuboids. The nitrogen removal rates were found to be significantly affected the characters of the layer as well as the biomass and roots of different plant species (P < 0.05). Correlations between pH, oxidation–reduction potential, and retention time indicated that nitrogen removal rates under study conditions mainly depended on the location of the layer and the plant species in the constructed wetland.