The principles of Gradient operator, Laplacian operator, LOG operator and Sobel operator are discussed. Certain features of breast can be extracted in different degrees and aspects from original images by applying four edge sharpening operators to the breast near-infrared imaging. A great number of cases prove that compared with the other three operators, the improved Sobel operator can effectively extract the structural features of the breast from an original image. It can be concluded that the improved Sobel operator can assist in diagnosing breast diseases.