Xitou Site, located in Xunyi County, Xianyang City, Shaanxi Province, contains rich human cultural relics from the Neolithic Age to the Ming and Qing Dynasties. In the excavation sites of Shangxitou Village and Nantou Village, many cave-dwelling sites of the Neolithic Age were found, and the floor of some of these sites was a Composite building material of “Baihuimian” (Lime layer) and organic-tempered daub, which were relatively well preserved. This paper used stereoscopic microscope, polarizing microscope, ultra-depth of field microscope and scanning electron microscope(SEM) to observe the structure of “Baihuimian and organic-tempered daub” floor. In order to further solve the problems of sample production materials, production process analysis and technical principle, the means of X-ray Diffractometer(XRD), Fourier transform infrared spectrometer (FT-IR), thermal analysis (TGA-DSC), energy dispersive spectrometer (EDS) were used to analyze and detect “Baihuimian”, organic-tempered daub and “Baihuimian and organic-tempered daub” floor. The results showed that the main ingredients of “Baihuimian” are silica dioxide and calcium carbonate obtained by carbonization of loess-doll after calcination; The “Baihuimian” has three layers, which should be smeared three times, and the thickness of each layer of “Baihuimian” is the same and not more than 1 mm; The substrate of “Baihuimian” is organic-tempered daub, in which the straw fiber can strengthen and inhibit cracking. When daubing the “Baihuimian”, the lime water infiltrated into the organic-tempered daub and calcium hydroxide itself was carbonated to produce calcium carbonate, contributing to organic-tempered daub structures stability and strength. The two building materials are still closely combined, with only a 10~20 μm distance between them, which indicates that at least in the late Neolithic Age, Chinese ancestors had widely mastered the compound building material and its construction technology. This study is of great significance to understanding and utilising natural materials by ancient Chinese ancestors and to sort out the development of traditional architectural science and technology civilization.