B2O3-K2O-MgO glasses with different concentrations of MgO (0-20 mol. % in the steps of 5) were prepared by melt quench technique. Structural characterizations of these glasses were conducted through FT-IR, DTA and density measurements. The amorphous nature of the glasses was checked by X-ray diffractometry (XRD). The transformation of BO3 trigonals to BO4 tetrahedral units has evidenced from the FT-IR spectra of the prepared glass samples and the BO4 units increases with an increasing concentration of MgO content. The transition temperature (Tg), melting temperature(Tm) and crystallization temperature (Tc) have been identified using DTA measurements. The transition temperature (Tg) increases with an increase of MgO content. Density of the glasses increases whereas molar volume decreases which reveals the compactness of the glasses. The structural properties of these glasses were discussed in terms of the relative proportion of potassium and magnesium oxides.