Abstract: We found that, in the isothermal treatment process of the amorphous Li+ conductor B2O3-0.7 Li2O-0.7 LiCl-0.1 Al2O3, the plot of the conductivity vesus time rises at first, then, after passing a maxium falls monotonically, and followed by two flat sections. It has been established that these phenomena are due to the phase sparation and crystallization of this amorphous material. In this work, we develop a view point of interface effect between different phases, i.e. we consider that there is a high conductivity layer at the interface between different phases and its contribution compensates or exceeds the decrease of conductivity caused by the bulk effect, of the crystallization. On the basis of this interface effect, an explanation about the above-mentioned experimental plot is given.