In the study, the reduced graphene oxide/graphitic carbon nitride sheet membrane (RGO/PDA/g-C 3 N 4 ) was fabricated by the dopamine modification and assembling the RGO/PDA/g-C 3 N 4 composites on the surface of commercial CA (cellulose acetate) membrane, consisting of an RGO/PDA/g-C 3 N 4 -CA composites membrane and RGO/PDA/g-C 3 N 4 free standing membrane. These membrane materials were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Atomic Force Microscope (AFM) and UV–vis diffuse reflectance spectra (DRS). The RGO/PDA/g-C 3 N 4 composites membrane achieve to continuous and simultaneous flow-through separation of oil/water emulsion and degradation of soluble organic dye under visible-light irradiation in a short time. The results demonstrate that the flux of RGO/PDA/g-C 3 N 4 composite membrane was strongly influenced by g-C 3 N 4 ratio. With the g-C 3 N 4 ratio increasing, the membrane flux was gradually improved, besides, the separation rate of oil/water emulsion and retention rate of MB (methylene blue) is about 99.5% and 99.8%, respectively. Most important of all, the composite membrane can keep steady flux and high separation and retention efficiency after 5 times of recycling under visible-light irradiation. The composite membrane investigated in this study hope to become an attractive way as promising candidate for water purification.