Protection and restoration of cultural relics are applicable to various disciplines such as archaeology, physics, chemistry, and biology. Conservators have always been interested in exploring a nondestructive test. Among these in situ analysis, terahertz technology has widely applied to various areas as an emerging subject in the past 20 years, including security check, drug quality supervision, semiconductors and so on. Recently, the application of terahertz imaging in the field of cultural security has become a popular topic. In this paper, a lacquer box is investigated through terahertz time-of-flight imaging. Experimental results demonstrate that the lacquer box has a bilayer structure. The completed wood material is considered to be the carcass, the surface of which is painted with different decorative patterns. In addition, terahertz time-of-flight imaging can be used to detect damage inside the carcass, i.e., the wood structure in the painted box.