The invention provides an air injection system for fire flooding oil extraction. The system comprises a first air compressor, a first buffer tank and a second air compressor which are connected in sequence, a third valve is arranged between the first buffer tank and the first air compressor, and a fourth valve is arranged between the first buffer tank and the second air compressor; the system further comprises a third air compressor, a second buffer tank and a fourth air compressor which are connected in sequence, a seventh valve is arranged between the second buffer tank and the third air compressor, and an eighth valve is arranged between the second buffer tank and the fourth air compressor; a first bridging pipeline is connected between the outlet ends of the first air compressor and the third air compressor, and a ninth valve is arranged on the first bridging pipeline; a second bridging pipeline is connected between the inlet ends of the second air compressor and the fourth air compressor, a tenth valve is arranged on the second bridging pipeline, and the outlet ends of the second air compressor and the fourth air compressor are connected with injection pipelines. According tothe air injection system for fire flooding oil extraction, central air injection into an oil well can be achieved, and it can be guaranteed that air injection construction is continuously conducted.