Embodiments of the present application provide a tissue boundary determination apparatus and method. The tissue boundary determination method includes acquiring multiple slice images of multiple positions of a tissue to be examined, determining, with regard to at least one first selected slice image of the multiple slice images, a tissue boundary on the first selected slice image, and determining, according to the tissue boundary on the first selected slice image, tissue boundaries on a predetermined number of other slice images adjacent to the first selected slice image. Therefore, an accurate tissue (such as malignant tumor) boundary may be acquired efficiently so as to provide a reference basis for analysis on internal and external tissue of a tumor.