Potassium-ion batteries (PIBs) are promising next-generation energy storage candidates due to abundant resources and low cost. Sb-based materials with high theoretical capacity (660 mAh·g^–1) and low working potential are considered as promising anode for PIBs. The remaining challenge is poor stability and slow kinetics. In this work, FeSb@N-doped carbon quantum dots anchored in three-dimensional (3D) porous N-doped carbon (FeSb@C/N⊂3DC/N), a Sb-based material with a particular structure, is designed and constructed by a green salt-template method. As an anode for PIBs, it exhibits extraordinarily high-rate and long-cycle stability (a capacity of 245 mAh·g^–1 at 3, 080 mA·g^–1 after 1, 000 cycles). The pseudocapacitance contribution (83%) is demonstrated as the origin of high-rate performance of the FeSb@C/N⊂3DC/N electrode. Furthermore, the potassium storage mechanism in the electrode is systematically investigated through ex-situ characterization techniques including ex-situ transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Overall, this study could provide a useful guidance for future design of high-performance electrode materials for PIBs.