The auto-generation mechanism of persulfate was introduced into an anodic oxidation system. The formation of persulfate and the degradation of Congo red in a double anode system consisting of Ti/Ru-Ir oxide coated and Pt anodes were investigated in this paper.The results indicated that there was a competition relationship between them in the anode zone.The double anodes were favorable for Congo red degradation and persulfate formation.The degradation rate of Congo red was proportional to anode current density at coated metal oxide anode and SO2-4concentration

but inversely proportional to pH.The yield of persulfate was closely related to the current density

SO2-4 concentration and pH.Among them the current density was main factor.SO2-4 could be transformed effectively into S2O2-8 only when the current density was higher over 200 times at Pt-anode than at Ti/Ru-Ir oxide coated one.The persulfate produced in the electrolysis system can decompose organics in the solution under irradiation of simulated sunlight.The degradation mechanism of combined sunlight and persulfate was also investigated.The results showed that there could be intermediate materials of quinonoids imine type during  degradation

which is of photosensitivity and more sensitive to visible light.So

it can induce photosensitive reaction under irradiation of visible light

resulting in generation of singlet oxygen1O2 and peroxy radical O-2·.These species can promote formation of hydroxyl radicals ·OH and sulfate radicals SO-4· at low pH（acidic)condition

which can produce the species with strong oxidizability and make this system easy degrade organics.