Aiming at the problem that median filtering will destroy image thin line features and edge blur-ring when denoising

filtering window of the appropriate shape and size is selected ac-cording to the edge features of the image to be processed

and the image is filtered. An im-proved median filtering algorithm which fuses edge gradient information is proposed. The algorithm can adaptively adjust the shape and size of the filtering window according to the edge gradient infor-mation to minimize edge blur and protect fine line features. The algorithm is applied to the bot-tom image of the shell with imprinting defect. The comparison of the images before and after filtering effectively proves that the proposed algorithm can well protect the defect features.