In order to realize the visualization and real-time tracking of the instruments in surgical navigation system, we use the CAD solid model of the instruments directly or by reverse engineering, and transform the solid model to surface model. Then, the instruments, which are fixed with locator, are characterized and tested their precision. After registration between the CT model and the patient site in intra-operation, the system accurately displays the STL model of the instruments according to the tracked site and orientations. The model construction of the instruments is the base of the surgical navigation and is important to improve the security and precision of operation.