An annular optical element assembly having a central axis includes a first annular optical element, a second annular optical element and a light blocking sheet. The first annular optical element includes a first central opening, a first axial connecting structure and a first inner receiving surface. The second annular optical element includes a second central opening, a second axial connecting structure and a second inner receiving surface. The second inner receiving surface surrounds the second central opening, wherein the second inner receiving surface is closer to the central axis than a second axial connecting surface is to the central axis, the second inner receiving surface is vertical to the central axis, and the first inner receiving surface and the second inner receiving surface are corresponding and not connected to each other for defining a receiving space.