This invention is a centering method for adjusting the aiming component and its connected element. The element can at least rotate around the 1st axis on a horizontal plane and a portion of the aiming component can at least rotate around the 2nd axis. Its characteristic is as follows: By mounting a device on the rotating element and radiating a collimated light beam on the rotating portion of the aiming component, an image point will be produced on the viewing end of aiming component. On moving the rotating element to different positions if the image point displaces, then adjast the connecting device between the rotating portion of the aiming component and the rotating element. To repeat the above steps for a series of oriented angles required until the image point moves only within the predeterminated range by rotating through the entire swing range of the rotating element.