The new zinc barium metaphosphate glasses (50−x)BaO–xZnO–50P2O5 with 0≤x≤50 were prepared and studied. An analysis of the infrared spectra, of molar volume and of the variation of glass transition temperature with the ZnO content is discussed in order to describe the structure effect of Zn2+ additions in these glasses. The density of (50−x)BaO–xZnO–50P2O5 glasses decreases continuously as the ZnO substitution increases, in accordance with the mass differences between BaO and ZnO. For x less than 30mol%, the glass transition temperature decreases by the decrease in phosphate chain length. For larger x (30≤x≤50mol%), the T g increase, due to the effect of the high field strength of the cations Zn2+ increased due to the increase in the amount of Zn2+ ions in the glasses, that results in tighter network formed by the shortened phosphate chain length.