FeF3•0.33H2O crystallizes in hexagonal tungsten bronze structure with more opened hexagonal cavities are considered as next generation electrode materials of both lithium ion battery and sodium ion battery. In this paper the mesoporous spherical FeF3•0.33H2O/MWCNTs nanocomposite was successfully synthesized via a one-step solvothermal approach. Galvanostatic measurement showed that the performances of sodium ion batteries (SIBs) using FeF3•0.33H2O/MWCNTs as cathode material were highly dependent on the morphology and size of the as-prepared materials. Benefitting from the special mesoporous structure features, FeF3•0.33H2O/MWCNTs nanocomposite exhibits much better electrochemical performances in terms of initial discharge capacity (350.4 mAh g–1) and cycle performance (123.5 mAh g–1 after 50 cycles at 0.1 C range from 1.0 V to 4.0 V) as well as rate capacity (123.8 mAh g–1 after 25 cycles back to 0.1 C). The excellent electrochemical performance enhancement can be attributed to the synergistic effect of the mesoporous structure and the MWCNTs conductive network, which can effectively increase the contact area between the active materials and the electrolyte, shorten the Na+ diffusion pathway, buffer the volume change during cycling/discharge process and improve the structure stability of the FeF3•0.33H2O/MWCNTs nanocomposite.