A　carbon-coated　K0.76V0.55Nb0.45OPO4　(KVNP@C)　polyanion　material　was　successfully　synthesized　by　a　simple　sol-gel　method.　The　KVNP@C　possesses　a　highly　stable　inorganic　open-framework　structure,　which　is　hard　to　be　affected　by　the　Na+　intercalation/deintercalation　when　used　as　an　anode　material　for　sodium-ion　batteries　(NIBs).　The　assembled　KVNP@C/Na　half-cell　shows　a　capacity　retention　of　81.2%　and　an　average　Coulombic　efficiency　of　99.8%　at　a　current　density　of　300　mA/g　after　1500　cycles.　In-situ　XRD　analysis　reveals　a　single-phase　solid　solution　reaction　mechanism　with　a　lattice　expansion　of　4.76%.　This　work　sheds　insights　into　the　quest　for　developing　novel　polyanion-based　anode　materials　for　sodium-ion　batteries.