The modeling of medical volume data has drawn public attention recently since traditional approaches, such as triangle tiling of the contour surface and 3D array of voxels, do not fit for the efficiently rendering, especially for rendering of vessel structure. In this paper, an algorithm for modeling vessel biomedical structure based on the extraction of medial-axis and the interaction of metaballs is proposed. The authors adopt distance transformation to extract the medial-axis, and use the metaball to describe the structure. The results show that this model not only remains the complicated topological structure, but also assures the smooth shape of rendering result.