Abstract: The ecological ditches are the key links of agricultural non-point source pollution control. In the present study, ecological ryegrass mats were developed independently and applied in ecological ditches. The removal effect for nitrogen in the simulated farmland drainage by floating ryegrass mat was discussed, and also the growth state of the plants. Results showed that, the growth state of ryegrass were best cultivating in compact mat plus 5 kg·m^-2 sieved fine soil. In the low influent nitrogen concentration stage of the flowing experiment (TN: 8.16 mg·L^-1), the removal rates of NH₄⁺-N were 56.8% and 40.5% in the treatment of high flow velocity (D1) and low flow velocity (D2), respectively, which were higher than Control-without plants in (25.6%). This is the result of denitrification and plant absorption. However, in the high influent nitrogen concentration stage (TN: 20.53 mg·L^-1), the removal rates of NH₄⁺-N dropped to 44.6% and 32.1% in the treatment of D1 and D2, respectively. In the whole stage of the flowing experiment, the average removal rates of TN were not high (13.1%-22.3%), and were not different significantly among top, middle, and bottom layers. Under the conditions of TN influent concentration of about 8.16 mg·L^-1 and influent flow of 1.5-2.5 L ·min^-1, the ryegrass grew better and the removal rates of NH₄⁺-N were higher. Therefore, the dense straw curtain covered with a certain amount of soil was chosen for seedling raising, it can be used for interception and purification of water polluted by low nitrogen load. In the future, the nitrogen removal efficiency can be further enhanced and the application potential can be improved by mixing other grass species or increasing the coverage of grass curtain floating bed.