This　research　studied　optical　and　structural　properties　of　SrO-Nb2O5-P2O5　glasses　containing　0-25　mol%　Nb2O5　and　35-60　mol%SrO　using　spectra　of　UV-Vis,　FOR　and　XPS.　Our　aim　was　to　work　new　moldable　glasses　which　are　colorless　with　high　refractive　index　and　transmittance,　and　their　correlation　with　glass　structure.　Nb2O5　plays　the　role　as　an　intermediate　of　glass　formation,　and　transforms　the　role　to　network-former　or　glass-modifier　depending　on　composition.　Refractive　index　increases　monotonically　with　Nb2O5　content　at　the　expense　of　transmittance,　and　specific　coloring　which　occurs　in　ternary　compositions　with　the　ratio　P2O5/SrO　＞　1.　This　effect　arises　from　much　increased　[Nb3+　and　Nb4+]　fraction,　as　quantitatively　deconvoluted　in　Nb3d　XPS　spectra,　in　the　ligand　[NbO6](octahedral)　which　is　supported　by　FTIR　and　O1s　XPS　spectra.　As　the　ratio　P2O5/SrO　＜=　1,　Nb2O5　is　more　of　a　network　former　and　[NbO6](octahedral)　structure　turns　into　[NbO4](tetrahedron)　with　partial　Nb-O-center　dot　center　dot　center　dot(Sr)　bonding　turns　into　(Nb-O-Nb)(tetrahedron),　coloring　disappears.　(C)　2010　Elsevier　B.V.　All　rights　reserved.