An image processing method based on the multi-scale morphology which focuses on the structural difference between dim target and background noise is presented. A better filtering effect can be got by choosing proper structure elements and morphological operators. The morphological filter is a new type of nonlinear filter developed from mathematical morphology. Structural information distilled from signal by use of morphological operation is determined by the form of structure element, since morphological operators in essence show the reciprocity between the aggregation of targets and structure element. Because of the mathematical preciseness and the simpleness, there is a particular advantage of mathematical morphology when it is used to describe the configurative characteristic of target image. The useful information and multi-level features from the images can be got by multi-scale analysis using morphological filters through changing the scale parameter of the structure elements.