We developed a simple X--assisted (X = Cl, Br, I) one-pot hydrothermal reaction to successfully synthesize a series of BiOX/Bi2WO6 heterojunction. The effect of different halogens and their addition amount on the photocatalytic performance of BiOX/Bi2WO6 composites was investigated using benzyl alcohol selective oxidation under visible-light irradiation. All BiOX could enhance the photocatalytic activity of Bi2WO6, but the BiOBr was the optimum for the maximum improvement of Bi2WO6. The match of energy band structure between BiOX and Bi2WO6 resulted in the highly efficient separation of photogenerated charges, which was mainly attributed to their fundamental distinction of the photocatalytic activity. This work clarified the essential distinction in photocatalytic performance of the different halogen of BiOX/Bi2WO6 heterojunction, and also provided guidance for the construction of efficient heterojunction photocatalysts.