The influence of heat treatment (100 °C, 150 °C, 200 °C, 300 °C, and 400 °C) on the structure and the zinc ion storage performance of V2O5·nH2O is explored. The results show that the interlayer water content, interlayer distance, and V4+ content in V2O5·nH2O can be regulated by heat treatment. Electrochemical characterization demonstrates that the as-prepared vanadium pentoxide without heat treatment shows rather poor cycling stability (only 56 m Ah g−1 after 600 cycles at 0.5 A/g). After being heat treated in the temperature range of 100 to 200 °C, the zinc ion storage performance of vanadium pentoxide can be enhanced dramatically. Particularly, the vanadium pentoxide after being heat-treated at 150 °C exhibits the best cycling stability (179 mA h g−1 after 600 cycles at 0.5 A/g), superior high-rate capability (117 mA h g−1 at 3.0 A/g), and faster electrochemical reaction kinetics. The results reported in this work could provide clues for regulating and optimizing the electrochemical performance of vanadium pentoxide as a cathode material for ZIBs.