Water pollution is a significant social issue that endangers human health. The technology for the photocatalytic degradation of organic pollutants in water can directly utilize solar energy and has a promising future. A novel Co3O4/g-C3N4type-II heterojunction material was prepared by hydrothermal and calcination strategies and used for the economical photocatalytic degradation of rhodamine B (RhB) in water. Benefitting the development of type-II heterojunction structure, the separation and transfer of photogenerated electrons and holes in 5% Co3O4/g-C3N4photocatalyst was accelerated, leading to a degradation rate 5.8 times higher than that of pure g-C3N4. The radical capturing experiments and ESR spectra indicated that the main active species are •O2−and h+. This work will provide possible routes for exploring catalysts with potential for photocatalytic applications.