Visualization of medical images has become an important method for the basic medical research as well as clinical diagnosis and treatment. Construction of the highly sophisticated three-dimensional (3D) models of the human body by computers has become an essential foundation for current medical research and disease treatment methods. Visualization Toolkit (VTK) is a kind of famous software in scientific visualization fields. It is convenient and efficient for programming. This paper implements three typical algorithms, Contour-connecting, Marching Cubes and Ray-casting, of medical image 3D visualization using VTK with VC++. Results show that VTK is a powerful tool with many advantages, such as simple operation, fast, and good interaction ability and can be widely used in 3D reconstruction of medical images.