Rare earth elements (REEs) are strategic resources for the development of modern society. However, their mining can cause nitrogen pollution in groundwater. In this study, a nitrification-sulphur autotrophic denitrification-enhanced permeable reaction wall (NSAD+PRW) was constructed to treat groundwater in rare earth mines and the feasibility of its engineering application was demonstrated. The results show that a maximum removal rate of 100 % was achieved for NO3−-N. The average removal content of NH4+-N was 27.15 mg/L and the highest TN removal content of total nitrogen (TN) reached 145.49 mg/L. The removal rates of most REEs exceeded 99.88 %. The composite filler provides a good environment for microorganisms, which also produce extracellular polymeric substances (EPS) to protect themselves during nitrogen removal. In addition, some nitrifying bacteria (Rhodanobacter and Nitrospira) and denitrifying bacteria (Thiobacillus, Sulfurovum, and Ferritrophicum) with high adaptability to rare earth mine groundwater were found. In conclusion, the results of this study provide an important reference for nitrogen removal from groundwater in rare earth mines with high engineering application significance.