The invention discloses a precious metal leaching agent and a method for for receiving precious metals from dead catalysts. The precious metal leaching agent consists of ionic liquid, trichloro isocyanuric acid or dichloro isocyanurice acid and a solvent, wherein the mass ratio of the ionic liquid to the trichloro isocyanuric acid or dichloro isocyanurice acid is 30: 1 to 5:1; the volume ratio ofthe solvent to the ionic liquid is 10:1 to 1: 1; the negative ions of the ionic liquid are selected from at least one of chloride ions, bromide ions, iodide ions, cyanide ions and dicyandiamide ions;and the positive ions of the ionic liquid are selected from at least one of pyrrolidine positive ions, quaternary ammonium salt positive ions and quaternary phosphonium salt positive ions. The invention provides a method for recovering precious metals from waste catalysts by utilizing the precious metal leaching agent. The precious metal leaching agent is economic, environment-friendly and efficient, and is capable of effectively harmlessly treating the waste catalysts and recovering the precious metals of the waste catalysts so as to realize the recycling of the waste resources, decrease theenvironment pollution and improve the social and economic benefits at the same time.