Abstract: Thiosulfate leaching is a promising non-cyanide leaching method in comparison with the conventional cyanide leaching method, because of its short extraction time, high extraction rate, low toxicity, environmental protection, etc. Based on the chemical properties of the thiosulfate, this paper discusses the oxidation effect of cupric ion, cupric-tetra ammine and oxygen, which is the key factor for the leaching rate and reagent consumption in the leaching process of silver using thiosulfate.