An alignment system includes a light source for emitting a light. An alignment mark is disposed on a substrate for receiving the light. The alignment mark includes a first pattern and a second pattern disposed on the substrate. The first pattern includes a first region and a second region. The second pattern includes a third region and a fourth region. The first region and the third region are symmetrical with respective to a symmetrical axis. The second region and the fourth region are symmetrical with respective to the symmetrical axis. The first region includes first mark lines parallel to each other. The second region includes second mark lines parallel to each other. A first pitch is disposed between the first mark lines adjacent to each other. A second pitch is disposed between the second mark lines adjacent to each other. The first pitch is different from the second pitch.