VTK, which is an open source free software system, can be applied to image processing, computer graphics and visualization in scientific computing, and it is widely used in all walks of life at home and abroad. This dissertation describes the basic composition, system architecture, and visualization process of VTK. Furthermore, it applies VTK to the visualization of medical images, uses a surface rendering- Marching Cubes algorithm- and a volume rendering- Ray Casting algorithm- to achieve 3D reconstruction of medical images under the Microsoft Visual Studio 2005, and has designed the system examples. Practice proves, using VTK to develop medical images’ reconstruction system has good reconstruction results, less development time and high code reuse rate.