Abstract The formation, thermal stability and crystallization mechanism of glasses in NaBO2-B2O3 system have been studied by means of thermal analysis, X-ray powder diffraction at high and room temperatures, and IR absorption spectra. The stable glasses are formed easily in this system. The crystallization processes are related to macroscopic state of samples. The crystallization temperature of bulk glasses is higher than that of amorphous powders. A part of components crystallizes as different phases. They melt directly at different temperatures. The crystal structure of crystallization products is close to glass structure.The ionic conductivity in NaBO2-B2O3 system was determined by ac impedance method. The conductivity of glasses are 2-3 orders higher than that of crystals with the same composition, while the activation energy of glasses lower than that of crystalline state for the same composition.