Abstract: According to the targets with different size s, different sizes of the filter modes need to be selected in image processing. Multiple targets with different sizes may be existed in an image, or the size of the target is not known at all in ATR system sometimes. Therefore, the filter with different sizes will be used to test in those situations. How to get the best results of the different filters together is a very important key technology in image processing. A method based on the improved DS evidence theory was presented. The experiment results indicate that the proposed method could well extract different sizes targets in an image.