The invention discloses an active element array substrate and a display panel. The active element array substrate comprises a substrate which is provided with at least one positioning mark; moreover, a black matrix is arranged on the substrate, covers the positioning mark, and divides a plurality of pixel areas on the substrate; a plurality of active elements are arranged corresponding to the plurality of pixel areas; and the active element array substrate limits the light transmission and optical density of the black matrix, wherein the black matrix can have high light transmission for a detection light source with long wavelength used by contraposition equipment, so that the contraposition equipment has good identification to the positioning mark. Meanwhile, for a display light source with short wavelength, the black matrix still has high optical density to maintain good display contrast. Besides, the positioning mark can consist of at least two layers of metal layers to increase the total thickness of the metal layers and enlarge a metal bevel taken as a mark pattern, so that the identification of the contraposition equipment on the positioning mark is improved.