Photo-Fenton method, the combination of Fenton reagent with light, is an efficient method for waste water treatment. In the present paper, the degradation of great green SF using this method was studied. Great green SF is a kind of permanent and nondegradable dye. Through numerous experiments, the influences of various parameters including the UV absorption curve of great green dye SF, the concentration-absorbency curve of great green dye SF, dosage of Fe2+, dosage of H2O2, initial pH, different light sources, and cation-exchange resin on the degradation were researched intensively. The optimum condition for dye SF degradation was given. Under the experiment condition, the sun light can promote this reaction apparently. The reaction time can greatly be shortened too. After the cation-exchange resin was introduced into the Fenton system, the activation of H2O2 can be enhanced to a great extent. The dosage of H2O2 will be decreased. The degradation effect of the great green SF is better. Under optimal conditions, the overall color removal is more than 96.7% within 40 min; COD can be removed effectively at the same time.