A transparent dielectric of the $PbO-B_2O_3-SiO_2-A1_2O_3$ system which was a low melting glass has been used for PDP (Plasma Display Panel), but it has a problem which is a reaction to be occurred between a transparent dielectric layer and electrodes (Ag, ITO) after firing. This research was conducted for ion migration of $Ag^+$ and $Sn^ {2+}$ during firing three different frits of low melting glass. The result showed that yellowing phenomena occurred through a chemical reaction between $Ag^+$and $Sn^ {2+}$ at 550~58$0^{circ}C$ for 20~60 min. In addition, it was confirmed that the migration of $Sn^{2+}$ from ITO electrode made a strong effect on the yellowing phenomena.