[Background] The treatment of low C/N domestic wastewater is difficult to meet the discharge standard. The integration of multistage A/O, bioaugmentation and biofilm can effectively solve this problem. [Objective] This study aimed to develop a pilot-scale multistage A/O with biofilm process, and domesticate efficient microbial agent for nitrogen and phosphorus removal to perform bioaugmentation in the system. [Methods] Chemical oxygen demand (COD), NH4+-N, NO3?-N, total nitrogen (TN) and total phosphorus (TP) in effluent of the pilot-scale plant and the full-scale wastewater treatment plant were measured and compared to analyze the removal efficiencies. Meanwhile, high through-put sequencing was used to examine the impact of bioaugmentation on microbial community structure. [Results] The removal efficiencies of COD, NH4+-N, NO3?-N, TN and TP in the pilot-scale plant were better than those in the full-scale wastewater treatment plant. The maximum removal rate of TN by the acclimated low-temperature aerobic denitrifying bacteria was 84.21%, when the phosphorus removal rate by the acclimated low-temperature denitrifying phosphorus accumulation bacteria was 85.75%. After bioaugmentation, the removal performance of COD, NH4+-N, NO3?-N, TN and TP was improved, when Pseudomonas for aerobic denitrification and denitrifying phosphorus accumulation obviously increased. [Conclusions] Multistage A/O with biofilm process showed an ideal performance on the treatment of low C/N domestic wastewater. Bioaugmentation can effectively improve the pollutant removal efficiencies of the system under low temperature.