The invention relates to the technical field of medical image analysis, and discloses an unsupervised segmentation method for multi-mode brain tumor MRI, which comprises the following steps of 1) inputting different modal images of a tumor patient, including T2 weighting, Flair and T1 enhanced images, and carrying out gray value normalization on the input images; and 2) extracting features of pixel points of the brain region on T2 and Flair images, classifying the pixel points by using a clustering fusion method, and automatically identifying the category of the tumor from a plurality of categories. According to the unsupervised segmentation method for the multi-mode brain tumor MRI, the imaging characteristics of different MRI modes are fully utilized; the information of different modes and neighborhood information are combined, so that the segmentation accuracy is improved; an unsupervised segmentation method is used, a large amount of labeled data is not needed, the long-time training time and complex calculation are not needed, so that a large amount of work is facilitated, the segmentation accuracy is effectively improved, and the purposes of being easy and efficient to implement and high in operation speed of the algorithm are achieved.