Sodium ion batteries are attracting ever-increasing attention for the applications in large/grid scale energy storage systems. However, the research on novel Na-storage electrode materials is still in its infancy, and the cycling stability, specific capacity, and rate capability of the reported electrode materials cannot satisfy the demands of practical applications. Herein, a high performance Sb2O3 anode electrochemically reacted via the reversible conversion-alloying mechanism is demonstrated for the first time. The Sb2O3 anode exhibits a high capacity of 550 mAh g-1 at 0.05 A g-1 and 265 mAh g-1 at 5 A g-1. A reversible capacity of 414 mAh g-1 at 0.5 A g-1 is achieved after 200 stable cycles. The synergistic effect involving conversion and alloying reactions promotes stabilizing the structure of the active material and accelerating the kinetics of the reaction. The mechanism may offer a well-balanced approach for sodium storage to create high capacity and cycle-stable anode materials.