In this study, we prepared Bi1-xBaxFeO3 MNPs (x= 0.03, 0.08, 0.12) via a rapid sol gel procedure to improve heterogeneous photo-Fenton catalytic degradation of toluene under visible light irradiation. We found that Ba-substitution in BiFeO3 magnetic nanoparticles (BFO MNPs) can play an important role in improving the photo-Fenton catalytic degradation of toluene from aqueous solution. Increasing the Ba doping level up to 12%, greatly affect in iron redox cycling and oxygens vacancies as compared to pure BFO MNPs. The iron redox cycling and existence of oxygen on the surface of Ba doped BFO had been affected by the photo-Fenton process. The scavenger effect evident from the study results confirmed that the photo Fenton catalytic degradation of toluene from aqueous solution was mainly controlled by the formation characteristics of hydroxyl radical ('OH) and also partially by the formation of other active species such singlet oxygen (102). The proposed radical reaction mechanism was also discussed. The degradation of toluene was partial in the dark but almost complete under visible light irradiation by the photo-Fenton catalytic degradation reaction. Bi1-x Ba-x FeO3 (x= 0.12) showed the highest photo-Fenton catalytic degradation efficiency with a toluene removal of 98%, total organic carbon (TOC) and chemical oxygen demand (COD) reduction of 85% and 94%, respectively, after 40 min of visible light irradiation. (C) 2016 Elsevier B.V. All rights reserved.