Aqueous alkaline batteries represent a promising kind of energy storage device, which hold great promise in power electronics with both high energy density and power density. However, their development is severely limited by their anodes which have unsatisfactory cycling stability. In this study, we report a new kind of oxygen vacancy activated Bi2O3 (Bi2O3-x) nanoflowers on carbon paper as robust anode in alkaline batteries via a hydrothermal growth and a following hydrogenation treatment. Owing to the enhanced charge transport rate after introducing oxygen vacancies, the resulting binder-free Bi2O3-x nanoflowers achieve a high capacitance of 0.97 mAh/cm2 at 4 mA/cm2 in a negative potential window from 0 to −1.2 V vs Hg/HgO, remarkably larger than the pristine Bi2O3 nanoflowers (0.6 mAh/cm2). Furthermore, this Bi2O3-x anode also owns excellent durability with a capacity retention of 73.8% after 5000 cycles. This work may contribute additional insight into the construction of high-performance anodes for alkaline batteries.