The　integration　of　lanthanide(Ln)ions　and　polyoxoniobates(PONbs)is　challenging,and　the　known　Ln-substituted　PONbs　are　still　scarce.This　work　introduces　high-nuclear　iso-Ln-oxo　clusters　into　the　PONb　system.The　first　series　of　high-nuclear　Ln-oxo　clusters　encapsulated　heterometallic　polyoxonio-bates　Hg[Na(H2O)4l[Cu(en)2]1o{Ln6(μ3-OH)6(SiNb18O54)3}·18H2O(1-Ln,en=ethylenediamine,Ln=Dy,Gd,Tb,Ho,Er,Tm,Yb,Lu)based　on　flower-like　{Ln6(μ3-OH)6(SiNb18O54)3}({Ln6Si3Nb54})clusters　have　been　successfully　synthesized　via　one-pot　hydrothermal　synthesis　strategy.The　flower-like　polyoxoanion{Ln6Si3Nb54}　is　consisted　of　three　heteropolyoxoniobate　{SiNb18O54}　clusters　and　one　unique　planar　equi-lateral　triangle-shaped　{Ln6(μ3-OH)6}　cluster,which　presents　the　highest　nuclear　iso-Ln-oxo　cluster　in　PONb　chemistry.In　{Ln6(μ3-OH)6}　cluster,each　pair　of　μ3-OH　groups　link　three　Dy3+ions　to　form　a　small　approximate　equilateral　triangle-shaped(Dy3(OH)2}　cluster.Furthermore,the　three　{Dy3(OH)2}　clusters　comprise　a　bigger　approximate　equilateral　triangle-shaped　{Dy6(μ3-OH)6}　cluster.The　reported　hexanu-clear　{Ln6}　cluster　skeletons　are　mostly　octahedral,however,such　equilateral　triangle-shaped　skeleton　of　the　hexanuclear　Ln-oxo　cluster　is　first　observed.The　1-Dy　exhibits　good　water　vapor　adsorption　capacity　and　ferromagnetic　properties.