Arsenopyrite is a common gold‑bearing mineral in gold ores, where gold particles are often encapsulatedas"invisible gold"within arsenopyrite, making efficient recovery challenging. The effect of Fe3+ addition on the oxidationbehavior of arsenopyrite in the copper（Ⅱ）-ammonia-thiosulfate gold leaching system was studied using electrochemicalmethods such as cyclic voltammetry curves, Tafel curves, and electrochemical impedance spectroscopy curves, combinedwith X‑ray photoelectron spectroscopy（XPS）characterization. Electrochemical results indicate that after the additionof Fe3+ , the oxidation peak of arsenopyrite shifts leftward with increased intensity, and the oxidation reaction potentialdecreases from 0.5-0.6 V to around 0.25 V. XPS characterization reveals that after adding the oxidizing agent Fe2（SO4）3, S0 appears on the arsenopyrite electrode surface; the content of Fe（Ⅱ）-AsS decreases, and the contents of As（Ⅲ）and As（Ⅴ）increase, further validating the electrochemical findings. This study confirms that the addition of Fe3+ inthe copper（Ⅱ）-ammonia-thiosulfate gold leaching system can effectively enhance the gold leaching rate fromgold‑bearing arsenopyrite.