Abstract: Aiming at the problems of high concentration of ammonia nitrogen, low biodegradability and difficult treatment in landfill leachate, using aged landfill leachate as model, the removal efficiency and the maximum processing load of ammonia nitrogen in the modified soil rapid infiltration system (SRIS) were investigated. Meanwhile, the concentration of ammonia nitrogen at different depths of the system was monitored. In addition, the microbial community distribution in the system before and after the treatment were analyzed by high-throughput sequencing technology. The results showed that when the influent concentration of ammonia nitrogen was about 125 mg/L, the hydraulic load was 0.11 m³/(m²·d), and the inflow frequency was once a day, the average concentration of ammonia nitrogen in the effluent was about 3 mg/L and the total removal rate was higher than 97.5% after treatment with primary and secondary percolation columns in the modified SRIS. When the hydraulic load increased to 0.22 m³/(m²·d), the total removal rate was 87.27%. When the frequency of inflow was changed to twice a day, the total removal rate was 96.17%. The maximum ammonia nitrogen removal of after treatment with primary and secondary percolation columns in the modified SRIS reached to 200 and 110 mg/L, respectively, and the degradation mainly occurred in the lower and bottom layers. The lower layer of the modified SRIS had the most diverse bacterial community. Proteobacteria was dominated at phylum level, and the relative abundance of Exiguobacterium was the highest at genus level, as well as the presence of a variety of nitrifying, denitrifying bacteria and planctomycetes, which make the main contribution to the removal of ammonia nitrogen in the system. This research demonstrated that the modified SRIS could effectively remove ammonia nitrogen from the landfill leachate, which provides a reference for the effective treatment of the aged landfill leachate.