Cost-effective, stable, and highly efficient heterogeneous catalyst is the key challenge for wastewater treatment based on Fenton-like advanced oxidation processes. Perovskite oxides offer new opportunities because of their versatile compositions and flexible physiochemical properties. Herein, a new strategy is proposed that is different from the frequently used alien-metal doping, to tune surface properties of perovskite oxides by nanocompositing perovskite with inert oxide, resulting in improved activity and stability for catalytic oxidation. By in situ modification of LaFeO 3 with inert La 2 O 3 oxide through one-pot synthesis, several important surface properties such as surface defects, H 2 O 2 adsorption capacity, Fe 2+ concentration, and chargetransfer rate were improved, as well as resistance against iron leaching. In performance evaluation, among the various materials, La 1.15 FeO 3 (L 1.15 FO) composite shows the highest Fenton activity (0.0402 min −1 ) for activating H 2 O 2 to oxidize methyl orange, 2.5 times that of the pristine LaFeO 3 . Notably, in situ electron paramagnetic resonance analysis and radical scavenging tests unveil a faster generation of singlet oxygen as the dominant reactive species over L 1.15 FO, consequently a novel non-radical activation mechanism is proposed. Such improved performance is assigned to the strong coupling effect between the nanosized LaFeO 3 and La 2 O 3 in the hybrids, which fine-tune the surface properties of LaFeO 3 perovskite as superior Fenton catalysts.