Ammonia stripping process consumes large amounts of alkali. The packed column is easy to scale and cause pressure drop. The tray tower has the disadvantages of discharge and the large fine droplets loss by entrainment. Besides, the absorption of ammonia nitrogen in the exhaust gas is incomplete. In order to solve the above problems, a twostage airrecirculated stripping process was developed and used in the gasliquid reactor to remove the ammonia nitrogen during anaerobic digestion of pig manure. A mathematical model focusing on the effects of controlling factors (gas flow rate, dose of alkali and gastoliquid ratio) on one response (ammonium nitrogen removal efficiency) was developed and fitted by response surface methodology (RSM). The results showed that the pH value could rise from 803 to 886 in 1h by stripping CO2. The alkalinity of anaerobic digestion was decreased from (8.953±297)mg/L to (8.283±21)mg/L. Stripping carbon dioxide was conducive to reduce the buffer capacity of anaerobic. The ammonium nitrogen removal efficiency could reach 96.78% (dose of lime 22.13g, gas flow rate 6L/min, gastoliquid ratio 3.000). The twostage airrecirculation process could be used to remove and recover ammonium nitrogen in anaerobic digestion of pig manure without pretreatment in this system. The RSM further optimized the twostage airrecirculation ammonia removal process. The developed gasliquid reactor could be used to remove ammonium nitrogen with airrecirculated stripping process.