The invention provides an application method of an additive in enhancing oxidization of arsenical gold mineral by bacteria. The additive is ammonium persulfate, and the dosage is 20-50% of total amount of the arsenical gold mineral. Two adding modes are adopted, the first adding mode is adding to a leaching system together with bacteria liquid, and the second adding mode is adding to the leachingsystem after bacterial leaching for a certain period of time. When the first adding mode is adopted, the additive mainly contains oxidized arsenical pyrite, the dosage of the additive is increased to50% from 0%, and the oxidation rate of the arsenical pyrite is increased to 95% from 8.7%. When the second adding mode is adopted, the additive mainly contains As(III) in oxidizing solution, the dosage of the additive is increased to 50% from 0%, and the oxidation rate of As(III) is increased to 91.12% from 4.9%. Reproduction and activity of the bacteria are not affected after the additive is added; the oxidation of the arsenical pyrite or As(III) can be obviously enhanced in an oxidization process; the problem of toxicity of a biological oxidation product can be solved, and the application method becomes an important measure for increasing the speed of oxidizing the arsenical gold mineral by the bacteria.