A　novel　quaternary　borate,　Na2.18K0.82SrB5O10,　has　been　prepared　by　high-temperature　solution　reaction　below　800　degrees　C.　Single-crystal　XRD　analyses　showed　that　it　crystallizes　in　the　triclinic　P　(1)　over　bar　group　with　a　=　7.3900(15)　angstrom,　b　=　7.6490(15)　angstrom,　c　=　9.773(2)　angstrom,　alpha　=　79.31(2)degrees,　beta　=　70.85(2)degrees,　gamma　=　62.09(1)degrees,　Z　=　2.　The　basic　structural　unit　in　Na2.18K0.82SrB5O10　is　a　double　ring　[B5O10](5-)　composed　of　one　BO4　tetrahedron　and　four　BO3　triangles.　The　[B5O10](5-)　groups　are　arranged　around　crystallographic　centers　of　symmetry　to　form　[B10O20](10-)　columns　that　are　held　together　by　Na+,　K+/Na+,　and　Sr2+　cations　via　electrostatic　interactions.　The　IR　spectrum　further　confirmed　the　presence　of　both　BO3　and　BO4　groups.　UV-vis　diffuse　reflectance　spectrum　showed　a　band　gap　of　about　3.80　eV.　Solid-state　fluorescence　spectrum　exhibited　the　maximum　emission　peak　at　around　337.6　nm.