The main objective of this study is to identify the feasibility of improving the nitrogen removal efficiency in low C/N wetlands by arranging aquatic macrophyte species with different phonological characteristics. We conducted a pilot experiment, adding warm-season species of Hydrilla verticillata to cold-season species of Oenanthe javanica at a floating-bed constructed wetland system (FCW), in order to quantify the effects of the decomposition of the warm-season macrophyte residue on the nitrogen removal efficiency under the condition of low temperature during autumn and winter seasons. The results showed that the adding of H. verticillata significantly increased the C/N ratios in the organic carbon shortage systems of FCW, and thus improved total nitrogen and nitrate nitrogen removal efficiency due to stimulating denitrification activities. During the four cycle periods of the phenophase-combined FCW, compared with the control group, the removal efficiency of total nitrogen in each period was increased by 23.03%, 10.90%, 18.55% and 22.93% respectively, and the removal efficiency of nitrate nitrogen was increased by 38.28%, 20.74%, 17.87% and 17.06%, respectively. Therefore we conclude that it is feasible to improve the nitrogen removal efficiency by re-arrangement of warm and cool season plants in the low C/N wetlands.