The invention relates to a method for preparing high-purity metal rubidium and cesium, and belongs to the technical field of nonferrous metal preparation. The method comprises the steps of uniformly mixing a nonferrous metal compound, a main reducing agent and an auxiliary reducing agent and carrying out thermal reduction reaction in an inert gas environment to obtain the high-purity nonferrous metal. According to the method, the purity of a prepared product such as rubidium and can reach more than 99.9%, the recovery rate is more than 95%, and the method has a good application prospect. Compared with an existing domestic production method, the method has the advantages that the time for industrial production of the metal cesium and rubidium is short and is shortened by at least 25%, the equipment requirement is extremely low, the manufacturing cost is greatly reduced and is reduced by at least 50%, and therefore the metal cesium and rubidium can be massively produced in an industrial mode in a short time.