Carved during the Northern Dynasties era, Luohan Grottoes are an important part of the 100-li (31-mile) Jingchuan Grotto Corridor. As an important historical and cultural heritage site on the ancient Silk Road, the murals of the grottoes boast rich content and special techniques, which are of great value for research on the development of Buddhism in Jingchuan and the civilization of the Silk Road. We have analyzed the materials and structural features of the murals. The results show that the structure of the murals from inside to outside is support, coarse plaster (straw added), fine plaster (cotton added), white ground layer and paint layer. The murals were painted many times. For interior murals, the red pigment is cinnabar, the green is atacamite and the blue is azurite. For exterior murals, the red pigment is red iron oxide, the green is emerald green, the blue is ultramarine, the orange one is yellow iron oxide and the black is carbon black. The workmanship of the murals is explained and the application of mural pigments is compared with that of other murals along the Silk Road, in order to promote the conservation and utilization of this cultural heritage.