The practical application of photocatalytic water splitting is essentially limited by the slow kinetic nature of the water oxidation process. Therefore, it is highly desirable but challenging to explore a low-cost and high-efficiency water oxidation catalyst for the aim of commercialization and industrialization. We herein report the first-time synthesis of a novel and high-efficiency visible-light-driven photocatalyst composed of flower-like Co(CO3)0.5(OH)·0.11H2O (CCO) nanowires and Bi2WO6 (BWO) nanosheets, i.e. CCO/BWO nanocomposite, via a facile hydrothermal method. Without utilizing any additional cocatalyst, the composite of CCO/BWO in 30% weight ratio exhibits extraordinarily high photoactivity and photostability towards O2 evolution, achieving an average O2 generation rate of 953 µmol h−1 g−1 under visible-light irradiation (λ > 420 nm).