Novel BiF3/BiOBr heterojunction photocatalysts were prepared from a fast and stable microwave-assisted method, and characterized by X-ray diffractometry, X-ray photoelectron spectroscopy, scanning electron microscopy, ultraviolet-visible spectroscopy and fluorescence spectroscopy. The photocatalytic activity of BiF3/BiOBr heterojunctions under light irradiation was significantly higher than pure BiOBr or BiF3, and was maximized at the Br:F molar ratio of 1:1, as the targeted 20 mg/L Rhodamine B (RhB) solution was completely degraded within 40 min. This was mainly because the unique BiF3/BiOBr heterojunction formed during photocatalytic degradation accelerated the photoelectron and hole separation, effectively enhanced the quantum efficiency, and thereby strengthened the photocatalytic activity.