Abstract: A background suppression algorithm based on the wave atom transform (WAT) is proposed to remove the complex background clutter in the detection technique of dim and small targets in infrared images. WAT is used to decompose the input image, and to extract multi-scale and multi-direction detail features of the original image. According to the difference between the target and background clutter signal, each coefficient of the WAT decomposed level is modified by the frequency domain adjustment function, then the predicted background image is reconstructed using wave atom inverse transform. Finally, the result image is obtained by subtracting the background image from the original image. Experimental results demonstrate that the proposed algorithm can highlight targets, improve signal-to-clutter ratio, and suppress complicated background clutter in infrared images with dim and small targets effectively when compared with the max-median and wavelet algorithms.