An The development of efficient and stable photocatalytic materials is the key to the application of photocatalytic technology. In this paper, urea, bismuth nitrate and potassium bromide were used as raw materials, BiOBr/g-C3N4 composite photocatalysts (Bix/CN) with different mass ratios were prepared by one-step hydrothermal method. Based on the results of UV-Vis, the calculated ECB values of BiOBr and g-C3N4 were 0.52eV and -1.1eV, while the calculated EVB values of BiOBr and g-C3N4 were 3.38eV and 1.55eV, respectively. Photoelectric catalytic performance tests showed that Bi3/CN had the higher photocurrent density and lower charge transfer resistance. When the visible light irradiation time was 10 min, the total removal rate of RhB by Bi3/CN was 81.35%. The total removal rate of RhB by Bi3/CN decreased only 6% after reused for 5 times, indicating that Bi3/CN had high and stable photocatalytic efficiency for RhB. The improvement of photocatalytic efficiency of compound photocatalyst mainly depended on the effective coupling of the two-dimensional monomers, and the effective interface contact improved the photogenerated electron transfer and carrier separation efficiency. The photocatalytic enhancement mechanism was proposed as that the accumulated electrons on CB of g-C3N4 for generation of ?O2- were the essential reason for the improvement of photocatalytic performance.