Abstract: The effects of two types of Cyperus alternifolius floating-beds-frame-bent compound ecological floating-bed (FCEFB) and traditional floating-bed (TFB)-on the removal of nitrogen and the community of nitrogen cycling-related bacteria in a eutrophic river were investigated in a greenhouse in an artificial pond with a volume of 1.5 m³. TFB is a traditional technology which uses a polyethylene foam board as a seedling bed to carry terraneous plants to reduce nitrogen, phosphorous and organic matter in contaminated water so as to purify water quality. FCEFB is a newly-developed floating-bed which uses a plastic hollow frame as a seedling bed, on which filters can be added in addition to planting terraneous plants. The results showed that: first, the removal efficiency of the FCEFB and TFB were significant in NH₄⁺-N by 91% and 86%, TN by 74% and 64% and NO₃^--N by 49% and 31%, respectively. Second, the two floating-bed systems effectively increased the microorganisms, in terms of both total number and population quantity of the nitrogen cycling-related bacteria in the water. The nitrogen cycling-related bacteria in the FCEFB were hundreds to thousands of times higher than those in the control at different sampling periods. Third, the number of nitrogen cycling-related bacteria had significant, linear correlation to the nitrogen removal from the polluted water. Relative coefficients of ρ(NH₄⁺-N) showed extreme, significant, positive correlation with the number of ammonifiers, and extreme, significant, negative correlation with the number of nitrobacteria. On the other hand, ρ(NO₃^--N) and ρ(TN) showed extreme, significant, negative correlation with the number of denitrifying bacteria. Fourth, the FCEFB was more efficient at nitrogen removal than the TFB due to its special structure. The contribution rate of nitrogen removal in the FCEFB was 18% by filter system absorption, 16.5% by plant uptake and 75.5% by the microbial system. In the TFB, the contribution rate of nitrogen removal was only 31.8% by plant uptake and 68.2% by the microbial system. It was concluded that plant uptake is only one method of nitrogen removal in floating-bed systems, and that biodenitrification via the microbial community may play a dominant role in the remediation of contaminated water in the two floating-bed systems.