Mixing elements on the B site in ABO<sub>3sub> results perovskite with narrow band gap. Ba<sub>2sub>FeNbO<sub>6sub> exhibits band gap of 2.29 eV by using two elements. SrTiO<sub>3sub>-Ba<sub>2sub>FeNbO<sub>6sub> solid solution displays a good visible light photocatalytic activity by promoting the charge separation process.