The selective oxidation of benzyl alcohol (BA) into benzaldehyde (BAD) is an attractive model reaction for organic synthesis. Using a microwave-calcination route, a novel flower-like Bi24O31Br10 with surface oxygen vacancies and bromine vacancies was successfully synthesized. In the construction of Bi24O31Br10, glucose acts as a complexing, reducing, and structure-directing agent. The as-synthesized Bi24O31Br10 exhibits excellent activity for the photocatalytic aerobic oxidation of BA into BAD, with > 99% conversion and > 99% selectivity under blue LED irradiation at ambient conditions, which is 3.3-, 4.7-, and 27.8-fold higher than that of TiO2, Bi4O5Br2, and Bi12O17Cl2, respectively. The high selectivity is due to the suitable energy band of the as-synthesized Bi24O31Br10 (E-g = 2.51 eV, valence band potential = +2.38 V), while the high conversion rate is largely due to the efficient separation of photogenerated carriers, surface defects, positively charge surface, and 3D micro/nano-architecture. The primary active species, including h(+), e(-), center dot O-2(-), and center dot OH, are all involved in the photoreaction. On the basis of experimental results and quantum-chemistry calculations, a direct hole oxidative mechanism with two-step dehydrogenation pathway was suggested. In addition, the as-synthesized Bi24O31Br10 catalyst remains stable during the photocatalytic process, indicating its potential for practical applications.