Abstract: Air flow rate and diffuser density are two important parameters of aeration system． In order to study the rules of oxygenation performance of fine-pore membrane and ceramic diffuser under different air flow rate and diffuser density on pilot scale research，oxygenation capacity and oxygen transfer efficiency were used as evaluation indexs． For the fine-pore membrane diffuser，the results showed that the oxygenation capacity increased with improving air flow rate and diffuser density． Oxygen transfer efficiency increased when air flow rate was from 0 to 3. 5 m3 /h，and then decreased when air flow rate was from 3. 5 m3 /h to 8. 0 m3 /h． As diffuser density increased，the oxygen transfer efficiency decreased first，then increased． For the ceramic diffuser，the results showed that the oxygenation capacity increased with improving diffuser density． Oxygen transfer efficiency decreased with air flow rate increased． As diffuser density increased，the oxygen transfer efficiency increased firstly， then decreased． The optimum air flow rate of single fine-pore membrane diffuser was about 3. 0 m3 /h and the optimum range of diffuser density was 4. 5% ～ 5. 0%， the optimum range of diffuser density of ceramic diffuser was 11% ～ 15%．