Display omitted •Carbon coating and Nb5+ substitution were simultaneously applied to modify Na3V2(PO4)3 composite.•Nb5+ doping could effectively enhance the electron conductivity of the materials.•The optimized material exhibits a high specific capacity and good cycling stability. Featuring favorable ion transfer and high thermal stability, NASICON-structured Na3V2(PO4)3 has been regarded as a promising cathode candidate for sodium-ion batteries. However, this material might be impeded by inferior rate capability owing to its disappointing electron conductivity. To address this issue, a combined technique of carbon coating and Nb5+ doping was carried out for the first time. On one hand, the coated carbon nano-shell could construct an electron-conductive network and buffer the volume stain. On the other hand, the introduction of Nb5+ into the Na3V2(PO4)3 crystal could regulate the relevant crystal parameters and create more vacancies, further facilitating the transfer of sodium ions. As a result, the optimized Nb-doped Na3V2(PO4)3@C material achieved an excellent performance of 81.6 mA h g−1 at 50C and a high-capacity retention ratio of 80.8% even after 1600 cycles. This work not only highlights the significance of carbon coating and Nb5+ doping, but also shows promising opportunities in potential cathode alternatives for sodium-ion batteries.