Structure of Li4SiO4-Li2WO4 and Li4SiO4-Li3BO3 glasses was studied by the Si-29 and B-11 solid state MAS-NMR spectroscopy. In the glasses Li4SiO4-Li2WO4, condensed structural units such as SiO3.53- and SiO32- were abundant at 40-60 3.5 mol% Li2WO4. Co-existence of condensed structural units reduced abundance of non-bridging oxygen and local charge on oxygen atoms, which might cause the enhancement of conductivity at 40-60 mol% Li2WO4. In the glasses Li4SiO4-Li3BO3, fairly small amounts of SiO3.53- were present compared with the glasses Li4SiO4-Li2WO4. From the change of quadrupole coupling constant of the three coordinated BO3 units, low symmetric BO3 units were found to be abundant in the glasses of 40-60 mol% Li3BO3, which was probably related to the enhancement of conductivity of glasses in the system Li4SiO4-Li3BO3.