Abstract: Micropolluted river and lake waters are typically characterized by low pollutant concentrations, limited carbon availability and strong water-quality fluctuations, which make stable pollutant removal difficult. Constructed wetlands (CWs) are widely used for micropolluted water treatment because they combine purification capacity with ecological benefits. However, the species-specific contributions of wetland plants and the rhizosphere microbial mechanisms that underlie these differences remain poorly understood. We established four horizontal subsurface-flow CW systems planted with Iris pseudacorus, Phragmites australis and Cyperus papyrus, together with an unplanted control, and operated them for 84 days using real micropolluted river water. By integrating water-quality analysis with 16S rRNA high-throughput sequencing and PICRUSt2-based functional prediction, we investigated the differential contributions of plant species to micropolluted water purification and the associated rhizosphere microbial mechanisms. The results showed that total phosphorus removal was governed mainly by substrate adsorption. Relative to the unplanted control, vegetation markedly enhanced the removal of total nitrogen and \mathrmNH_4^+ -N and also improved COD_Mn removal, although the contribution patterns differed among plant species. Iris pseudacorus made the greatest contribution to total nitrogen removal, with an average removal efficiency of 46.54%. Cyperus papyrus showed the best co-removal performance for \mathrmNH_4^+ -N and COD_Mn, with removal efficiencies of 53.80% and 79.09%, respectively. Although Phragmites australis did not show the highest overall removal efficiency, it was more effective in maintaining stable system performance. Microbial analyses showed that plant roots substantially reshaped rhizosphere community structure, driving the microbial community from a relatively dispersed and diverse state towards a more dominant and functionally specialized assemblage. Proteobacteria and Actinobacteriota remained the dominant phyla throughout, while taxa associated with organic matter degradation and nitrogen transformation, including Sphingomonas and Paracoccus, were significantly enriched in plant rhizosphere. Functional pathways related to carbohydrate metabolism were also enhanced. These findings suggest that different plant species selectively enrich functional microbial groups through root-derived carbon inputs, oxygen release and rhizosphere microenvironment regulation, thereby generating distinct pollutant-removal pathways. This study provides a theoretical basis for plant selection and functional enhancement in constructed wetlands for micropolluted river and lake water treatment.