This paper describes the structure of glass melts in the Nb2O5-B2O3-K2O system by high-temperature Raman spectra. Because the authors had adopted a special high- temperature heating apparatus in our experimental work, the Raman spectra of the glass melts can be directly measured in the high-temperature state. The experimental results indicate that the groups of (NbO6)and (NbO4) will replace (BO3) and (BO4) and compose a new structural network by introducing Nb2O5 into boric glass. The (NbO4) belongs to the Td group; it has two IR activity modes and four Raman activity modes. The Nb in the structure is SP3 hybridized orbital and also has one residual electron; it belongs to the (NbO4) and forms a large (pi) bond. Under the influence of the heating field, the (pi) bond is very easy deformed. The Raman matrix element of (NbO4) in the 870 cm-1 is zero, but the dipole transition matrix element is comparatively stable. This shows that the structure skeleton does not collapse. The (NbO6) belongs to the Oh group; it loses Oh group symmetry in the high-temperature state, so the new scattering peaks appear. This research is very useful for the study and production of a new series of optical glasses. Through this work, the structural model of nioboborate glass melts had been established.