In order to understand the mechanism of the ionic conductivity enhancement during pre-crystallization process, we have performed 7Li NMR investigations on amorphous ionic conductor Li2B2O4. The temperature dependence of 7Li NMR spectra is studied. It is found that 7Li NMR spectra in crystalline, amorphous samples and amorphous sample with small amounts of crystallites are very different from each other. An additional peak is observed to overlap 7Li NMR absorption line on amorphous sample with small amounts of crystallites. This phenomenon is similar to that in LiCl (or LiI) containing dispersed secondphase particles. 7Li NMR investigations on amorphous ionic conductor B2O3-0.7Li2O-0.7LiCl is also made, the results are similar to that mentioned above. It is concluded that they are all caused by the interfacial effect between amorphous matrix and the crystallites.