Effects of ryegrass floating-bed on the multiply of nitrogen cycling bacteria and removal of nitrogen in synthetic municipal wastewater were investigated in an artificial 1.5 m3 simulating pond in a facilitated greenhouse in order to figure out a suitable pathway to remove nitrogen from the wastewater. The results showed that the total nitrogen (TN) and NH3-N removal rates by the ryegrass floating-bed were 31.6% and 43.0% respectively. The Rhizosphere and the region beneath the root system were the most suitable places for the growth of nitrogen cycling bacteria.The total nitrogen cycling bacteria in the ryegrass floating-bed system reached the highest lg(A/(CFU?mL-1)) value of 8.82 at 16d, which was 3 to 5 order of magnitude higher than that in the control. At the same time, the presence of ryegrass significantly increased the community diversity of the nitrogen cycling bacteria, in which ammonifiers, nitrobacteria, nitrosobacteria and denitrifying bacteria were detected. Taken together, we proposed that the important pathways of ryegrass floating-bed to remove nitrogen from the wastewater were nitrogen absorption and assimilation by ryegrass and biodenitrification by microorganisms.