Abstract: A micro-disseminated primary gold ore was taken as the research object and the gold-bearing pyrite was pretreated with the nano iron powder (nZVI)-ammonium persulfate (APS) system before treated with a non-cyanide leaching agent. The reaction path of oxidized pyrite enhanced by the intermediate SO₄⁻∙ produced by nZVI-APS system, was calculated by quantum chemical calculation. The results showed that the leaching rate of gold reached 87.93% under the conditions of APS dosage of 4 kg/t, nZVI dosage of 4 kg/t, pretreatment time of 4 h, NaOH dosage of 10 kg/t, leaching agent of gold cicada dosage of 10 kg/t, and leaching time of 2 h. Notably, quantum chemical calculations revealed that the reaction path of oxidation pretreatment of pyrite in the nZVI-APS system was the first transition state (TS1) → intermediate (IC) → second transition state (TS2), where TS1 was the rate-controlling step for the production of SO₄⁻∙ in the system. Specifically, Fe²⁺ adsorbed with the S atom, O atom, and O bridge bond in APS, with the adsorption bond on the O bridge bond exhibiting the most stability. Additionally, the SO₄⁻∙ could oxidize Fe and S in pyrite, with Fe serving as the main active site.