Oily sludge carbon-based materials (OSC-X, X represents the calcination temperature, 500,600,700,800 and 900 °C, respectively) were prepared by pyrolysis method, and SEM, EDS, XRD, and XPS were used to analyze the microscopic morphology and elemental valence of the materials. On the degradation of p-nitrophenol (PNP) by OSC-800/PMS/GA, the effects of various systems, the temperature at which the carbon-based materials were pyrolyzed, the mass concentrations of gallic acid (GA) and peroxymonosulfate (PMS), the initial pH of the solution, the reaction temperature, and the concentration of pollutants were examined，the mechanism of PNP degradation by OSC-800/PMS/GA was explored. The findings demonstrated that the valence cycle between Fe3+ and Fe2+ and the surface hydroxyl groups on OSC-800 were involved in the activation of PMS and that adding GA greatly accelerated OSC-800 of catalytic degradation of PNP. The degradation rate of PNP by this system (OSC-800/PMS/GA) at 100 min was 88.14%, and the degradation process was consistent with the quasi-primary kinetic model. These conditions included an OSC-800 mass concentration of 2 g/L, a solution initial pH of 6.7, PMS molar concentration of 1.4 mmol/L, GA molar concentration of 0.25 mmol/L, PNP mass concentration of 20 mg/L, and a reaction temperature of 25 °C. There was a 2.42-fold increase in the degradation rate constant of PNP compared to the OSC-800/PMS system, a 1.65-fold increase in the COD elimination rate, and a 2.94-fold increase in the PMS utilization rate. Four kinds of reactive oxygen species (ROS), SO4??, ?OH, ?O2? and 1O2 were produced during the reaction.