Abstract: The visualization of medical 3-D data is a main application of Scientific Visualization. The properties of the Visualization Toolkit(VTK) are introduced in this paper. The principle and method of 3-D medical visualization system development based on the VTK are given. With a series of section images, the 3-D medical images are reconstructed successfully based on the VTK. Also the 2-D images can be browsed one by one and their statistic histogram is realized. The experimental results shows that VTK is easy to use and has powerful functions and is an effective visualization tool for medical 3-D data.