To investigate the differences in nitrogen removal contribution and the influencing factors of soils around typical plant roots in the riparian zone of the Third Drainage Ditch in Ningxia, Phragmites australis (Cav.) Trin. ex Steud., Bassia scoparia (Linn.) A. J. Scott, and Iris lactea Pall. in the riparian zone of the Third Drainage Ditch were taken as research materials, the denitrification and anaerobic ammonium oxidation rates, nitrogen removal contributions, and related influencing factors of soils around plant roots were analyzed by using the 15N isotope tracer method. The results show that the NH⁺₄-N content, NO^-₃-N content, NO^-₂-N content, total organic corbon content, total nitrogen content, and C/N ratio of soils around P. australis roots are significantly (P<0.05) higher than those of soils around I. lactea and B. scoparia roots, while the pH value and electrical conductivity of soils around B. scoparia roots are significantly higher than those of soils around P. australis and I. lactea roots; the richness and diversity of denitrification bacteria in soils around the three plant roots are higher than those of anaerobic ammonium oxidation bacteria. The denitrification rates of soils around P. australis, I. lactea, and B. scoparia roots are 2.397, 2.137, and 1.479 μmol·kg^-1·h^-1, respectively, the anaerobic ammonium oxidation rates are 0.650, 0.479, and 0.405 μmol·kg^-1·h^-1, respectively, and the denitrification nitrogen removal contribution rates (78.52%-81.70%) of soils around the three plant roots are all greater than those of anaerobic ammonium oxidation (18.30%-21.48%). Soil denitrification rate and anaerobic ammonium oxidation rate show significant or extremely significant (P<0.01) positive correlations with NH⁺₄-N content, NO^-₃-N content, total organic carbon content, and water content, while showing significant or extremely significant negative correlations with pH value and electrical conductivity. The relative abundances of dominant genera of denitrification bacteria Luteitalea, Nitrososphaera, Gaiella, and Rubrivivax, and anaerobic ammonium oxidation bacterial genera Candidatus Brocadia and Candidatus Jettenia show significant or extremely significant positive correlations with the corresponding nitrogen removal rates. The abundance of the denitrification functional gene nirS and the anaerobic ammonium oxidation functional gene AMX16S show significant positive correlations with the corresponding nitrogen removal rates. In conclusion, denitrification is the main nitrogen removal pathway in soils around plant roots, with soils around P. australis roots having the highest nitrogen removal rate, and soil physical and chemical properties, microbial communities, and their functional genes jointly regulate the soil nitrogen removal process.