Ferroelectric perovskite oxides [KNbO₃]_1−x[BaCo_1/2Nb_1/2O_3−δ]_x(KBCNO, δ>0 means the existence of oxygen vacancies) solid solutions (0.1≤x≤0.5)were successfully synthesized by doping Co and Ba into the lattice of KNbO₃ though solid-state reaction. The band gap energy of KBCNO shifts down to 2.4 eV and became visible-light-active due to the doping affection on the energy band structure comparing with that of wide-band-gap semiconductor KNbO₃ (3.4 eV). The X-ray diffraction and Raman spectra revealed that the KBCNO solid solutions are in perovsite phase and gradually transiting from orthorhombic to cubic structure with the different BaCo_1/2Nb_1/2O_3−δ (BCNO) contents. The reduction of band gap value makes KBCNO ferroelectric a promising candidate for photovoltaic materials.