Abstract: In order to reduce the recombination rate of graphite phase carbon nitride (g-C₃N₄) photocatalyst′s electron and holes, the Bi₂MoS₂O₄/g-C₃N₄ heterojunction was successfully prepared by the impregnation method. The absorption edge of the modified catalyst is red-shifted from 470 nm to 490 nm as measured by ultraviolet-visible diffuse reflectance spectroscopy. The effects of loading ratio, catalyst dosage and pH on the visible light degradation rate of Rhodamine B were discussed. When the mass ratio of Bi₂MoS₂O₄ to g-C₃N₄ is 18wt% and the catalyst dosage is 0.36 g/L, the catalyst can completely degrade Rhodamine B within 15 min. Free radical capture experiments and energy band analysis results show that the system has formed a type II electron transfer mechanism, the main active species is •O₂⁻.