The microbe-assisted air flooding is a new oil displacement method. Its mechanism is that the rate of microbial growth and metabolism can be increased by the help of oxygen in the air，which makes air flooding safer. Experiments of microbe growing and oxygen consumption were conducted under different initial concentrations of dissolved oxygen，and experiment of oil removing efficiency of the microbe under different concentrations of dissolved oxygen as well. The results show that the growth of experimental strains experience lag phase，logarithmic phase，stable phase and degenerating phase under conditions of oxygenation and non-oxygenation. When the initial concentration of dissolved oxygen is 4.5 and 5.5 mg/L，the maximum concentration of the microbial growth is 3 times of that under non-oxygenation；the concentration of dissolved oxygen declines logarithmically at the logarithmic phase，and that declines linearly at the stable phase and degenerating phase. The decreased oxygen in the oil reservoir is due to the oxygen consumption caused by microbe degeneration，and oil removing efficiency of the microbe may increase along with the increase of the initial concentration of the dissolved oxygen. Base on the law of oxygen consumption of the microbe and reservoir flow，mathematical model was set up to calculate the oxygen concentration distribution in the oil reservoir under different injection parameters. The result shows that the oxygen concentration decreases exponentially with increased reservoir radius；the whole well area have sufficient oxygen concentration for microbe growing and the reservoir has become a favorable environment for microbe；and the oxygen concentration in the air is reduced to safe level for air flooding and the minimum oxygen consuming radius is about145 meters.