Abstract:Qutan Temple in Qinghai Province is a well preserved official architectural complex of the early Ming Dynasty, which integrates ancient architecture, sculpture, color painting and wall painting. The wall paintings of Qutan Hall are of precious materials representing the early Ming Dynasty wall painting art and Buddhist art archaeology. The existing wall paintings of Qutan hall, which have an area of about 217.5 m2, are the classic early Ming Dynasty Tibetan Buddhist wall paintings in the Central Plains. They were analyzed by means of optical microscopy (OM), cross sectional analysis, scanning electron microscopy with energy dispersive spectrometry (SEM-EDS), X-ray diffraction (XRD), etc. The results of this study show that the wall paintings of Qutan Hall are supported by a brick wall, and that the ground layer is composed of a coarse mud layer and a fine mud layer. The sand content of coarse mud layer is about 60%, while that of fine mud layer is less, about 16%~25%; the total fiber content in plaster is about 3%; the particle size distribution of plaster soil is good, and the particle size is mostly concentrated in the range of 1~100 μm; the plaster contains a small amount of sodium sulfate and sodium chloride; the pigments used in the wall paintings of Qutan Hall are lead, cinnabar, chalcopyrite, parachalcopyrite, stone blue and other mineral pigments; the thickness of the pigment layer is between 20 and 200 μm; the layered application of red lead pigment in Qutan Hall is “lead below, vermilion above”, and shows the phenomenon of lead discoloration. In the wall paintings of Qutan Hall, there is no white ground in Ming Dynasty portion, but there is a white ground from the Qianlong period of the Qing Dynasty. This analysis and research presents information of the Qutan Hall layer structure of wall paintings, the composition of the plaster and the use of pigments, which provides important scientific data for the scientific conservation and further study of the Qutan Hall wall paintings.