Abstract: To reveal the mechanisms of the surface crystal salt and erosion of pottery jar, the super depth of field microscopy (DM), X-ray diffraction (XRD), ion chromatography (IC), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) had been used to analyze the salt precipitation. The results show that the main composition of the crystak salt were sodium chloride (NaCl), which caused the pottery efflorescence and decay. The sodium chloride mainly came from soil and groundwater, the storeroom dust was also a source of the salt. The temperature and humidity of the storage environment varied greatly, which were triggers of the occurrence of the salt on the pottery jar. The effect of salt on the pottery were studied by the analysis of salt crystallography and saturation solubility. The results show that the change in relative humidity had a greater impact on the concentration changes of NaCl compared to the temperature change in the storage environment of the pottery jar. The main factor causing the pottery efflorescence and decay is crystallization stresses brought about by NaCl, based on which protective suggestions were put forward.