A method for preparing a pure silver coating with high sulfate resistance through vacuum non-cyanide electroplating specifically comprises the steps of preparation of a non-cyanide pure silver solution, surface treatment of a copper matrix and vacuum plating of the silver coating. The pure silver coating prepared through the method has excellent sulfate resistance and is not discolored when beingsoaked in a 5% Na2S solution for 12 hours, and the sulfate resistance meets the aviation standard of QJ485-1988; and the pure silver coating has good binding force which meets the national standard ofGB/T 5270-2005. In addition, the prepared pure silver coating has the characteristics such as excellent conducting performance, heat conduction performance, abrasion resistance and long mechanical life. The pure silver coating prepared through the method has good combination properties and has high application value in outdoor high voltage isolators used in atmospheric environment, especially inhigh humidity, high salt and high sulfur environment of seaside-orientated industries.