To better understand the mechanisms of hydrogen peroxide (H₂O₂)’s decomposition and reactive oxygen species (ROS)’s formation on the catalyst’s surface is always a critical issue for the environmental application of Fenton/Fenton-like reaction. We here report a new approach to activate H₂O₂ in a co-catalytic Fenton system with oxygen incorporated MoS₂, namely MoS_2−xO_x nanosheets. The MoS_2−xO_x nanosheets assisted co-catalytic Fenton system exhibited superior degradation activity of emerging antibiotic contaminants (e.g., sulfamethoxazole). Combining density functional theory (DFT) calculation and experimental investigation, we demonstrated that oxygen incorporation could improve the intrinsic conductivity of MoS_2−xO_x nanosheets and accelerate surface/interfacial charge transfer, which further leads to the efficacious activation of H₂O₂. Moreover, by tuning the oxygen proportion in MoS_2−xO_x nanosheets, we are able to modulate the generation of ROS and further direct the oriented-conversion of H₂O₂ to surface-bounded superoxide radical (·O₂⁻_surface). It sheds light on the generation and transformation of ROS in the engineered system (e.g., Fenton, Fenton-like reaction) for efficient degradation of persistent pollutants.