The invention relates to a treating method of arsenic-containing copper slag, and belongs to the technical field of wet metallurgy. According to the treating method of the arsenic-containing copper slag, the mass percent of copper is 10% to 70%, the mass percent of arsenic is 5% to 20%, and the mass percent of iron is 5% to 30%; dilute sulphuric acid is added into the arsenic-containing copper slag to be evenly stirred to form ore pulp; and an oxidizing medium is added into the ore pulp for reacting until the pH value of the ore pulp is 1 to 3, sediment and solid-liquid separation are carried out, and copper-rich leaching liquid and arsenic iron slag are obtained. By means of the method, the process that valuable metal such as copper, zinc and indium is leached to a solution and the process that the arsenic and the iron form the stable arsenic iron curving slag are carried out synchronously, and the beneficial effects of being high in metal recovery rate, simple in process flow, clean and efficient in treating process and the like are achieved.