Characteristics of small targets in infrared array sensor image are studied and a new method for detecting small infrared targets through one single frame is put forward to solve the problem of low signal noise ratio（ SNR） target. Firstly

an improved median filtering is used to restrain isolated noise; Secondly

the image is decomposed by lifting wavelet and background is suppressed by morphology; Finally

small targets are detected by adaptive threshold to carry out binarization segmentation. Results of experiment show that this method can detect infrared small targets by array sensor effectively.