Photocatalytic process using core–shell nano-catalyst is an efficient, eco-friendly, and cost-effective process for removal or minimize hazard of pollutants in waste water. Herein, a recyclable and robust Cu2O/Fe3O4@C/Cu core–shell nanocomposite with photocatalyst activities is designed based on the synergistic photocatalytic activities of Cu2O and Cu and the magnetic property and stability of Fe3O4@C. The Cu2O/Fe3O4@C/Cu is shown to act as nano-catalyst to almost completely convert 4-Nitrophenol (4-NP) to 4-aminophenol (4-AP) within 3 min by sufficient electrons in the electron-rich region formed under ultraviolet light irradiation. The Cu2O/Fe3O4@C/Cu nanocomposite shows a good stability, reusability and magnetic separation ability after five recycles. In addition, a photocatalytic mechanism of 4-NP reduction over this nanocomposite is proposed, and the roles of each nanocomponent of this nanostructure played in the synergistic enhancing photocatalytic performance via cascade reaction is demonstrated. This work suggests that Cu2O/Fe3O4@C/Cu nanocomposite with high activity, good stability and magnetically recyclability could be applied for the elimination of pollutants in wastewater.