Pulsed high-voltage discharge, one of the advanced oxidation processes, was used for the treatment of Sunset Yellow wastewater. The effects of discharge type, initial pH, conductivity, and bubbling gas type on the formation of H2O2 were investigated in the mechanism experiments using deionized water. The concentration of H2O2 formed in hybrid series discharge mode was higher than that formed in hybrid gas-liquid discharge and liquid discharge modes. Moreover, a pH of 1 and low conductivity were beneficial to the formation of H2O2. Bubbling O-2 could obviously enhance the generation of H2O2. Afterwards, the effects of discharge type, initial pH, and bubbling gas type on the formation of H2O2 were also studied in the degradation experiments of Sunset Yellow. The experiment results were consistent with the mechanism experiments. Fenton reaction happened by the introduction of Fe2+ into the discharge process, which obviously enhanced the degradation of Sunset Yellow. Besides, the effects of initial pH and Fe2+ concentration on the Sunset Yellow degradation followed the second-order kinetics. Moreover, the degradation efficiency of Sunset Yellow with copper mesh as an electrode was much higher than that with the needle electrode. This article proposed a feasible approach to deal with Sunset Yellow wastewater.