Abstract: The aim of Sythetic Aperture Radar (SAR) imaging is to detect, identify and track the target in the complicated scene. In the paper, a new method is proposed to detect the man-made target in the complicated background. First, the improved Lee filtering algorithm using information entropy is proposed to eliminate the effect of noise and keep the detailed characteristic; then, a threshold-based segmentation technique is employed to do a cursory target detection in the high-resolution SAR image; finally, the characteristic (the size and the shape) of target is picked up based on the Directed Gradient Power (DGP). After above operation, the target is accurately detected. Meanwhile, the measured data is used to validate the effectiveness of the method.