Add an Empty and Parent it to the path with Follow Path then Alt-O. Select the camera and in F7 give it a slight TimeOffset, so it follows the Path slightly behind the Empty. Select the Camera first and then the Empty and Ctrl-T, TrackTo Constraint and the camera will always look at the Empty.
yes i knoew that but ai want the camera to follow a preset path (like a tunnel) if i parent it to the empty how could i make the camera follow the path?