As a kind of green tea extract with reducing and chelating properties, epigallocatechin-3-gallate (EGCG) was introduced into Fe²⁺-activated peroxydisulfate (Fe²⁺/PDS) system to accelerate the transformation fromFe³⁺ to Fe²⁺ and enhance the degradation of orange G (OG). The effect of PDS dosage, initial concentration of OG, initial solution pH, Fe²⁺ dosage, EGCG dosage, and co-existing anions on degradation of OG was investigated. The results demonstrated that Fe²⁺, EGCG, PDS alone, and EGCG/PDS, Fe²⁺/EGCG system showed poor effectiveness on degradation of OG, while the involvement of EGCG into Fe²⁺/PDS system enhanced OG degradation significantly:from 30.89% to 83.71%. Besides, the degradation efficiency of OG increased along with the dosage of PDS and Fe²⁺, and decreased with the increase of initial OG concentration. An optimum dosage of EGCG was found at 40 μmol/L and the degradation efficiency of OG performed well in a wide pH range of 2.0~7.0. The degree of inhibition from strong to weak follows the order of PO₄^3- > CO₃2-> Cl^-. Furthermore, by adding two typical radical scavengers (TBA and MeOH), hydroxyl radical and sulfate radical were identified to be responsible for OG degradation and SO₄^·- made the predominant contribution.