The removal of color, dye and dissolved organic carbon by Fenton discoloration was investigated using the synthetic dye wastewaters containing various dyes (reactive blue 19, Eriochrome Black T or Fast Green FCF). The results indicated that discoloration of dyes was very rapid but mineralization of dyes was insignificant based on the removal of dissolved organic carbon. The rates of color, dye and dissolved organic carbon removal were in the order of reactive blue 19 > Fast Green FCF > Eriochrome Black T. The generation of SO(2-)4, and N(O-)3, increased with the progress of the Fenton reaction. The concentrations of SO(-2)4 and N(O-)3, generated are in the order of reactive blue 19 > Fast Green FCF> Eriochrome Black T. A mathematic model was proposed to formulate the formation of SO(2-)4 and N(O-)3 during dye degradation. Results indicated that one S-containing and two N-containing functional groups are involved in the oxidation reaction, and that S-containing groups are involved in the oxidation reaction earlier than N-containing functional groups.