In this work, the Prussian blue/g-C3N4 (PB/g-C3N4) composite was synthesized from Prussian blue and g-C3N4 via a simple method. The composite was characterized by using X-ray diffraction, Fourier-transform infrared spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy. The material’s photocatalytic performance was studied via the degradation of rhodamine B (RhB). The results show that the composite degraded RhB more than pristine Prussian blue under visible light after 60 min. This material is promising for organic waste treatment