Abstract: In order to grasp the effect of pyrite on the Fenton technology treatment process of organic pollutants wastewater，using malachite green that is common organic pollutants in wastewater as the research target，with pyrite as catalyst，the Fenton reaction factors tests were conducted and also its reaction mechanism was analyzed.The results showed that the optimum conditions are concentration of malachite green 1 g/L，pH value 5.2，pyrite particle size -360 mesh with dosage of 5 g/L，H₂O₂ concentration 30% with dosage of 5 mL/L，reaction temperature at 30 ℃ and oscillation reaction(120 r/min) time for 3 h，and the degradation of malachite green reached 98%.The reaction mechanism showed that H₂O₂ was generated to highly activity hydroxyl radical · OH in the presence that oxygen in acidic environment is catalyzed by pyrite and the ·OH can oxidize and break the conjugated molecular structure of malachite green which have the ability of coloration.This action makes the malachite green become organic molecules with colorless，non-toxic side effects.

Key words: Pyrite, Fenton reaction, Malachite green, Decolorization