Some Jun Porcelain samples in Jin and Yuan dynasty, that have a thin layer of substance between glaze and body, were analyzed by EDXRF (energy dispersive X-ray fluorescence) line scanning technology, to study the character of thin layer between glaze and body of Jun Porcelain. The result shows that the chemical composition of the thin layer is just between that of glaze and body. So it is concluded that this thin layer between glaze and body is a reaction layer which formed in the process of porcelain fire. Meanwhile, it is revealed that the K₂O content of reaction layer is higher than those of glaze and body, and this phenomenon is different from those of other oxides. It is concluded that the phenomenon that the K₂O content of reaction layer is higher than that of glaze and body, is the synthetical result of several factors, including the content of SiO₂ and Al₂O₃ content in glaze and body, the structural character of glass, and the effect and speciality of SiO₂, Al₂O₃ and K₂O in glass, but not the result of the only factor that the penetrating capacity of K^＋ is strong.

Key words: Jun porcelain, reaction layer, chemical composition, line scanning analysis, EDXRF