[Objective] This study focuses on the practical demand for advanced nitrogen and phosphorus removal from the tail water of urban wastewater treatment plants. Aiming at the problem of low carbon-to-nitrogen ratios in urban wastewater treatment that result in unsatisfactory nitrogen removal efficiency, this study investigates the effects of different combinations of emergent plants and composite substrates on nitrogen and phosphorus removal from tail water through experiments. The application potential of natural manganese sand as a substrate is evaluated, providing theoretical and practical support for the optimization of constructed wetland technology and the resource utilization of manganese ore. [Methods] Three emergent plants, Acorus calamus L., Iris wilsonii C. H. Wright, and Scirpus validus Vahl were selected. Three experimental groups were established based on pairwise plant combinations, including Gp1 (Iris wilsonii C. H. Wright + Scirpus validus Vahl), Gp2 (Iris wilsonii C. H. Wright + Acorus calamus L.), and Gp3 (Scirpus validus Vahl + Acorus calamus L.). A composite substrate without plants was used as the blank control group (BC). The composite substrate consisted of natural manganese sand, zeolite, and ceramsite mixed at a ratio of 1∶3∶1. Constructed wetland systems were built using transparent polyethylene cylindrical columns with a height of 500 mm and a diameter of 160 mm to simulate the tail water treatment process of wastewater treatment plants. The experiment lasted for 70 days. During the experimental period, water quality indicators including total nitrogen, total phosphorus, ammonia nitrogen, and nitrate nitrogen were measured regularly. High-throughput sequencing was used to analyze the structure of microbial communities in plant root zones. [Results] All three plant combinations effectively removed nitrogen and phosphorus pollutants from the tail water, and the Gp3 group (Scirpus validus Vahl + Acorus calamus L.) showed the best performance. The total phosphorus removal rate reached 93.2%, the total nitrogen removal rate was 77.7%, the ammonia nitrogen removal rate was 91.7%, and the nitrate nitrogen removal rate was 70.6%. Pollutant concentrations in all experimental groups decreased rapidly during the first 30 days and then tended to stabilize, while the purification performance of the blank control group was significantly poorer. Microbial community analysis showed that the Gp3 group exhibited the highest microbial diversity and richness, with a Shannon index of 7.24 and unique OTUs accounting for 69.15%. The dominant phyla were Proteobacteria and Bacteroidetes, which together accounted for nearly 80%. Among them, Gammaproteobacteria played a key role in the denitrification process, and its relative abundance in the Gp3 group reached 29.2%, which was the highest among the three groups. [Conclusion] The synergistic effects of plant combinations and root-associated microbial communities in constructed wetlands are the key to efficient nitrogen and phosphorus removal, and the combination of Scirpus validus Vahl and Acorus calamus L.performs particularly well in advanced tail water treatment. The composite substrate containing manganese sand shows potential application value, while the specific mechanisms by which it promotes plant growth and microbial community formation still require further investigation. This study confirms the optimal purification performance of the Scirpus validus Vahl and Acorus calamus L. combination and the potential application value of manganese sand as a substrate, providing a reference for plant selection and targeted microbial cultivation in constructed wetlands for wastewater treatment plant tail water.