In order to study the characteristics of the lime layers in Tang tomb murals, seven Tang tomb lime layer samples, including one from Qianling, were analyzed with ultra-depth field microscopy, scanning electron microscopy, X-ray diffraction, thermal analyzer and strength tester to determine their macroscopic and microscopic structures, chemical makeup and mechanical strength. Results show that the lime layers are mainly composed of inorganic substances such as calcium carbonate, silica and magnesium dolomite. The average content of inorganic and organic substances is 88.7% and 9.3% respectively. The thickness is between 3 mm and 5 mm and the average pore diameter is about 1.77 [micro]m with roughly 7920 holes per mm2; The breaking strength is around 0. 96 MPa. Furthermore, the ratio of' inorganic to organic substances was in inversely correlated to its porosity. A small diameter, low moisture content and the presence of magnesium dolomite seem to contribute to an increase in strength. This study not only extends the research on the characteristics of Tang tomb mural lime layers, but also provides a scientific basis for more suitable infiltration and strengthening materials and for technologies that can be used in later restoration efforts.