Method for aligning optical system by hologram and apparatus thereof

An optical alignment system and method for aligning the various elements. In this method, a hologram element are formed so that the test beam traveling in an incident optical path of the same process. A holographic optical element and an element mounted in a lens barrel. Alignment error of the optical element according to the interference pattern is measured by the test beam and the reference beam is formed on an imaging surface. The optical element is aligned to remove the alignment error. Thus, alignment errors of the optical system can be measured and precise manner in real time.