Composite Bi@Bi2O3 microspheres have been synthesized via a microwave-assisted solvothermal route. The Bi@Bi2O3 microspheres had a narrow size distribution in the range 1.2–2.8 mm. Glucose was selected as the reductant, BiCl3 as the bismuth source, and ethylene glycol (EG) as the solvent in the synthesis system. The as-synthesized sample was characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), particle diameter distribution, energy dispersive X-ray spectroscopy (EDS), ultraviolet-visible (UV–vis) spectroscopy, and photoluminescence (PL) spectroscopy. The photocatalytic activities of the Bi@Bi2O3 microspheres were evaluated by the photodegradation of rhodamine B (RhB) and methyl orange (MO) dyes under UV light irradiation. The degradation reached ~96.6% for RhB and 100% for MO after 4 h reaction in the presence of the as-synthesized Bi@Bi2O3 microspheres.