Abstract:A two-stage coupled nitrogen removal system of Partial Nitritation (PN) / Anaerobic Ammonium Oxidation (ANAMMOX) was constructed. The nitrogen removal performance and microbial community structure of rare earth ammonia nitrogen wastewater treated by coupling system were studied. The effect of rare earth elements on the activity of functional microorganisms for nitrogen removal was investigated. The results show that the two-stage PN/ANAMMOX reactor can be successfully started by controlling dissolved oxygen, When the concentration of rare earth element Y(Ⅲ) in the influent is more than 10 mg/L, the nitrogen removal performance of the two-stage PN/ANAMMOX coupling system will gradually decrease, the performance of Y(Ⅲ) cannot be restored after the addition of Y(Ⅲ) is stopped. At the same time, the short-term experiments show that when the concentration of Y(Ⅲ) is more than 40 mg/L, the activity of AOB (Ammonia Oxidizing Bacteria) is inhibited. When the concentration of Y(III) is more than 20 mg/L, the activity of ANAMMOX is inhibited, and the inhibitory effect is enhanced with the increase of Y(Ⅲ) concentration. High-throughput sequencing indicates that the impact of rare earth element Y(Ⅲ) can decrease the abundance of AOB (Nitrosomonas) and ANAMMOX bacteria (Candidatus_Kuenenia), and the effect on Candidatus_Kuenenia is stronger than that of Nitrosomonas.