Based on the Michelson interferometer, optical coherence tomography (OCT) is a fast, non-contact, coherent optical imaging technology. OCT can image the internal microstructure underneath the surface. Archaeological objects are valuable and thus require nondestructive testing techniques. OCT, as a non-destructive analysis technique, is suitable for testing any part of the mural and other cultural relics. High resolution OCT images can provide the detailed information of the paint layer on the surface and the ground layer underneath the surface, which is elusive for traditional techniques. The technique of OCT is introduced and the verification experiment of the mural of Tang dynasty is carried out. From OCT images, defect information of the paint layer on the mural topside and structure underneath the surface can be seen. The information is of great help to the research and repair of the mural. OCT can be used in the research and repair of murals as a powerful tool for the researchers.