In order to scientifically analyze the composition of the black pigment on the west wall at the Eastern Gate Tower of Han Yang Mausoleum and further discuss the usage of pigments in Han imperial mausoleums, we adopted super depth field microscopy, scanning electron microscopy and energy dispersive spectrometry (SEM-EDS), map scanning technologies and X-ray diffraction (XRD), as well as a reference to relevant literature to make scientific analysis and in-depth discussion. The results show that the black component is copper oxide, which was caused by the oxidation of the original copper-containing blue-green pigment. This paper provides a scientific basis for subsequent pigment identification of painted cultural relics. That is, not only were modern analytical and testing means used to analyze and identify pigment species in their current state, but also it is pointed out that their color presentation forms are scientifically based on the environmental changes of the cultural relics. In addition, the map scanning of SEM-EDS technology can clearly identify the distribution of pigment particles, so it has incomparable advantages in microscopic analysis of pigment particles.