Aiming at infrared time-sensitive weak and small target detection in air-ground background, a practical detection method is proposed.Firstly, the fast adaptive bilateral filter is used to preprocess the infrared image, so as to smooth the edge information and eliminate the noise.Secondly, the high-pass filter with a template of 3×3 is adopted to suppress the large-area background of the infrared image.Then, according to the gradient characteristics, the multi-step eight-direction gradient method is applied to further eliminate the high-frequency background information.Finally, the adaptive threshold segmentation method is used to extract the infrared time-sensitive weak and small targets.The experimental results show that the proposed method has good robustness and performance for infrared time-sensitive weak and small target detection in air-ground background.