Porous h-MoO3@C nanofibers with a large specific surface area of 400.2 m(2) g(-1) were successfully synthesized with hot HNO3 oxidizing MoO2@C nanofibers without obvious damage to carbon shells. As anodes for lithium ion batteries (LIBs), the porous h-MoO3@C nanofibers electrodes show a reversible capacity of 302.9 mA h g(-1) at 2 A g(-1) after 500 cycles. As anodes for sodium ion batteries (SIBs), they also can deliver a good rate capacity and hold 108.9 mA h g(-1) at 2 A g(-1) after 500 cycles, even can have 91 mA h g(-1) at 5 A g(-1) after 1200 cycles. The excellent electrochemical performances of the porous h-MoO3@C nanofibers are attributed to the unique structure which not only can maintain the structure stability but also provide enough active sites for Li+/Na+. At the same time, the tunnel structure of h-MoO3 can lead to separate electron-hole and offer a great deal of special positions for cation (Li+/Na+) insertion/extraction. The present method may be helpful for the synthesis of transition metal oxides (TMOs)-carbon composites with high valence metal atoms in the field of batteries and catalysts.