The commonly used benzophenone-3 (BP-3) as ultraviolet filter ingredients is an endocrine-disrupting chemical that has received particular attention owing to its environmental ubiquity, and it poses a threat to aquatic biota and human health. In this study, novel α-Bi2O3@g-C3N4 nanocomposites with different α-Bi2O3 contents and enhanced photocatalytic activity were synthesized by a mixing calcination method. The as-synthesized photocatalysts were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, N2 adsorption/desorption isotherm analysis, electrochemical impedance spectroscopy, photoluminescence spectroscopy and electron paramagnetic resonance (EPR) spectroscopy. The 1 wt% α-Bi2O3@g-C3N4 composite exhibited the highest rate constant of 0.42 h-1 for photocatalytic degradation of BP-3, which was up to 6.3 times higher than that of g-C3N4 (0.07 h-1). The enhanced photocatalytic activity might be due to the enhanced separation of photogenerated electron-hole (e--h+) charge pairs and suppression of e--h+ recombination. Scavenging experiments suggested that •OH, h+ and •O2- worked together in the α-Bi2O3@g-C3N4 photocatalytic process. The EPR spectra demonstrated that the α-Bi2O3@g-C3N4 composites generated considerably more •O2- and •OH than g-C3N4. Finally, cyclic degradation experiments showed the reusability of 1 wt% α-Bi2O3@g-C3N4 for BP-3 removal.