The mural is an extremely important type of cultural heritage in China, with historical, artistic, scientific, cultural,and social value. The paint layer is the core value of the mural cultural relic, which contains important information and connotation of the ancient history and culture, religious belief, political economy, science and technology. The conventional and research methods are divided into nondestructive in-situ analysis and micro damage sampling. Although the sampling analysis method can satisfy the research of this precious and fragile cultural relics, the number of samples obtained is limited, and it causes irreversible damage to the noumenon. This paper uses digital imaging and spectral analysis to analyze the material and technology of the paint layers of Xianrenya grottoes in Tianshui. The results show that orthographic image can record the texture morphology information of the murals. Colorimeter can quantify the color of the pigments. Infrared-ultraviolet photography can extract hidden information such as drawing lines and repairing traces of murals wich are not easy to detect under visible light.High-power digital microscope can observe the micro morphology of the mural surface and the hierarchical information of damaged parts. Portable X-ray fluorescence spectrum can detect the color elements in the murals. After comparing the data collected by Hyperspectral with the standard spectrum, the mineral types of the pigment can be accurately determined. Therefore, using various kinds of nondestructive in-situ analysis can reduce the direct intervention on cultural relics and achieve the purpose of understanding the material and technology of the paint layers of murals. These non-contact and non-destructive testing methods can study the color, physical and chemical properties of the paint layer of murals systematically. They are all important and rapid means of nondestructive and in-situ analysis murals. They can be widely used in the study of grottoes, temples and tombs.