Abstract: In the multistage imaging proc ssing for SAR digital imaging and the applications of SAR image, it is often required to extract the luminance edge features of the SAR imagery. It has been studied to extract the luminance edge features for the ordinary imagery-produced by visible or infrared imaging system The methods using gradient are effectivery for the extraction of the luminance edge features of the ordinary imagery and commonly used. Because the serious noise of coherent speckle exists in the SAR imagery, some people believe that edge extraction using gradient for SAR imagery gives poor results. However in this paper, a rather ideal method is derived for the extraction of luminance edge features for SAR imagery with the consideration of the characteristics of SAR imagery. This method uses the relative average gradient and combines detection with tracking.