A kind of system and method for executing operation in the target site limited by virtual objects. Surgical navigation systems include patients tracker (54,56) to be attached to patient. Locator (44) cooperates with patients tracker and generates locator data associated with target site during operation. Surgical navigation systems further include the sighting device (72) for generating image data associated with the surface around target site and target site. The navigational computer communicated with locator and sighting device is configured as determining the region to be avoided except target site based on locator data and image data. In some cases, the second virtual objects are generated to limit the region to be avoided, so that the surgical operating instrument used during operation avoids the region.
