The method for segmenting malignant halo of malignant breast tumor in ultrasound image is useful in providing evidence for the differential diagnosis of breast tumor. In this respect, we adopt an improved anisotropic diffusion filtering method to preprocess the breast tumor ultrasound image, and then apply an improved LBF model with combination of Otsu and morphology methods to extract internal and external contours for obtaining malignant halo based on LBF model proposed by Li. We compare our data of malignant halo with doctor's manual-sketched malignant halo, and make quantitative analysis. The result shows that the malignant halo segmented by the proposed methods in this paper is in accordance with the manual-sketched malignant halo.