Abstract: A suitable method is proposed for detecting and tracking dim target in IR image sequence with low contrast and moving background. According to the correlation of moving background and position continuity of the moving target, the movement of background is computed with image matching. Complicated background is removed. Target is detected and tracked through adaptive prediction and threshold segmentation. Sequence images of one hundred frames with dim target are processed. The experimental results show that the method can automatically detect the target and track it effectively and steadily.