Abstract-Taking rural domestic wastewater in SouthernChina as the experimental object, the removal efficiency of CODcr, ammonia nitrogen and total nitrogen in different stages of the biofilm reactor and aeration conditions was studied by using the experimental simulation method in the A 2 /O 2 process. The results showed that: First, this process is fast in biofilm culturing, but the removal efficiency of ammonia nitrogen and total nitrogen removal efficiency is not high. Biofilm culturing starts 17d or so, the removal efficiency of CODcr can reach more than 80%. Second, after the normal operation process, the removal efficiency of CODcr and ammonia nitrogen was stable by this device, CODcr average removal rate was 80%, the average ammonia removal rate was 75%, this process has good anti shock loading capability, and the device good stability. Third, in the process of 6h and 2h interval aeration conditions, ammonia removal efficiency was higher and more stable, had been able to reach in the "Urban Sewage Treatment Plant Pollutant Discharge Standard" level emission B standard for first class discharge standard, the removal efficiency of CODcr was better. Fourth, comprehensive energy consumption and removal efficiency, the best aeration conditions in this process was 6h aeration and 2h interval. Operating under such conditions, the minimum cost per ton of sewage treatment. New sewage process A 2 /O 2 biofilm reactor designed to deal with the rural domestic wastewater in Southern China, which is characterized by less land occupation, low energy consumption, high pollutant removal efficiency, nitrogen removal function very well, simple management, the effluent can meet the discharge standard.