MnO 2 /TiO 2 core-shell structure photocatalyst was prepared by a two-step microwave method. Under visible light irradiation, this core-shell photocatalyst exhibited enhanced catalytic activity for the degradation of organic dye Rhodamine B and the oxidative removal of gaseous heavy metal Hg 0 . The MnO 2 shell not only enhanced the visible light absorption of TiO 2 , but also increased its specific surface area to 227.94 m 2 g −1 . In addition, the formation of core-shell heterojunction promotes the migration of carriers and the separation of photo-generated electron-hole pairs, and improves the stability of the composite, thus enabling it to exhibit enhanced photocatalytic performance. • MnO 2 /TiO 2 core-shell structure photocatalysts were prepared by a two-step microwave method. • MnO 2 /TiO 2 core-shell structure improves visible light absorption capacity, specific surface area and carrier separation. • MnO 2 /TiO 2 core-shell structure catalysts show photocatalytic activity to Hg 0 and RhB under visible light. This study provides an effective idea for the rapid preparation of high-efficiency core-shell photocatalysts, and is expected to contribute to the treatment of organic pollution in water and purification of metallurgical flue gas.