Abstract: The circulation reflux in nitrification liquid of sewage plant usually adopts slurry pump, which indirectly limits the adjustment range of circulation reflux ratio due to the limited number of installed tables. It is difficult to achieve accurate circulation reflux when the water quality fluctuates greatly.By changing the number of air risers, air lift reflux can be adjusted accurately under multiple working conditions.Experiments were carrried out to simulate the circulation reflux conditions in the sewage plant. Then the influence of ventilation q, pipe length L and pipe diameter d on the lift performance of the air lift pump under the conditions were studied.The results show that the fitting curve of the delivery Q and the ventilation q presents a parabola, and the efficiency of the pump decreases significantly after the peak value. Increasing the submerged ratio is helpful to increase the delivery, and the slope of DN100 curve is larger than that of DN80. It is better to choose the proportion of pipe length and pipe diameter with small length-diameter ratio (\fracLD \le 50). When the submergence ratio is 0.7, 0.75, 0.8, 0.85 and 0.9, the lift efficiency curve continues to decline with the increase of air flow rate, and the efficiency decreases with the increase of submergence rate. Fluent model was established, and the simulation results were consistent with the experimental results. This indicates that the experimental results were accurate.