Li3V2(PO4)3 (LVP) was evaluated as a promising cathode material for sodium-ion batteries (SIBs). The three-dimensional graphene frameworks wrapped LVP (LVP-G-FD) exhibited high energy density of 501.3Whkg−1, which is almost the highest energy density among the known polyanionic cathodes for SIBs. The enhanced electrochemical performance of LVP-G-FD is attributed to the graphene framework which provides the fast electronic transport network and buffering space. Besides, the sodium-ion storage mechanism of LVP was investigated via in-situ XRD and so on. The sodium-ion storage process is composed of the electrochemical topotactic replacement and the subsequent topotactic reaction.