Tang Sancai is an important cultural heritage of China. The analysis of the chemical compositions and phase structures of the Tang Sancai body and glaze is helpful to studying the Tang Sancai raw materials and firing technologies. This paper reports the analysis results of chemical compositions and phase structures of the Tang Sancai from the Liquanfang Kiln, the Huangye Kiln, and modern products from the Shaanxi Provincial Museum by the micro X-Ray fluorescence spectrometer and the X-ray diffractometer. The results show that the raw materials of Tang Sancai bodies in the Liquanfang kiln and Huangye kiln come from different clays. The cristobalite (PDF 76-0932) and α-quartz (PDF 46-1045) are the main phase structures in the Tang Sancai bodies of Liquanfang kiln and Huangye kiln. However, a small number of α-Fe2O3 (PDF 16-0653) phase andtraces of mullite (PDF 83-1881) phase existed in the Tang Sancai bodies of Liquanfang kiln and Huangye kiln, respectively.It shows that the difference in the firing technology and raw materials of the two kilns results in the different mineral structures of the bodies. In the glaze of Tang Sancai, the coloring elements Fe, Cu, and Co in the glazes melted in the lead flux, and Fe and Cu blended in the mixed area of the yellow glaze and the green glaze. The XRD patterns of the glazes show that there are mainly amorphous glass phases and traces of α-quartz (PDF 46-1045) in the glass. In addition, a small amount of Pb8Cu(Si2O7)3 (PDF 31-0464) phase existed in the Tang Sancai green glaze of Liquanfang kiln; a large amount of CaAl2Si2O8(PDF 89-1462) phase existed in the Tang Sancai yellow glaze of Huangye kiln; a small number of α-Fe2O3 (PDF 47-1409) phase existed in the Tang Sancai yellow glaze of Liquanfang kiln. It indicates that the differences in the chemical compositions of the glaze raw materials and the firing technologies lead to the different mineral crystals in the Tang Sancai glazes. The concentrations of the main elements of the modern products’bodies and glazes are close to the Huangye kiln samples. However, there are significant differences between the fake and true Tang Sancai in the phase compositions of the bodies and glazes. In general, the combination of micro X-ray fluorescence and X-ray diffraction analysis technology could have broad application prospects in raw material origin, authenticity identification, and firing technology of ancient ceramics.