Aiming at the problem of gray level quantization for aircraft infrared image,a method of gray level quantization for aircraft infrared image based on automatic low frequency gain limiting(ALFGL)is proposed.Firstly,the problems of gray level quantization are analyzed.According to the research of ALFGL circuit,a new gray level quantization method is proposed.The infrared image simulation results indicate that the proposed method can adapt to the high dynamic range of infrared radiation,and the infrared image can reflect the high and low temperature radiation characteristics clearly.