The invention relates to a preparation method for a copper and silver core-shell powder electric contact material, and belongs to the technical field of electric contact material preparation. Aiming at the problem that an existing Ag/Sn2 electric contact material is overhigh in resistivity and has poor anti-arc erosion performance, the invention adopts a technical scheme that short circuiting is caused due to the fact that silver ions can easily migrate under a direct current power-on condition or a hot and humid condition, so that the surface of nanometer copper powder is plated with silver, and then ball milling is performed on the nanometer copper powder plated with the silver and ceramic fiber prepared from lanthanum nitrate, strontium nitrate, ethylene glycol and a citric acid solution to prepare a composite material, and then, the composite material is heated and fired to prepare an electric contact material; migration ability of the silver ions is reduced by compounding copper with the silver. The copper and silver core-shell powder electric contact material prepared by the preparation method disclosed by the invention has relatively high fusion welding resistance and relatively good contact performance and anti-arc erosion performance, is prolonged by 10 to 15 percent in service life, has a simple preparation process, and is green and environmental friendly.