The high-temperature sodium-ion batteries (SIBs) used for large-scale energy storage have attracted extensive attention in recent years. However, the development of SIBs is still hampered mainly by their poor charge/discharge efficiency and stability, necessitating the search for appropriate electrodes. A simple potassium ion intercalation process is used herein to obtain the potassium vanadate (KV3O8) nanobelts. When serving as the anode for SIBs at a high temperature (60°C), the KV3O8 nanobelts display superior sodium storage performance with a high capacity of 414 mA h g−1 at 0.1 A g−1, remarkable rate capability (220 mA h g−1 at 20 A g−1), and super-long cycle life (almost no capacity fading at 10 A g−1 over 1000 cycles). Moreover, the ex-situ X-ray powder diffraction reveals no structural changes throughout the whole charge/discharge process, which further confirms their outstanding stability, indicating KV3O8 nanobelts are a promising candidate for high-temperature SIBs.