The invention discloses a method for preparing metal lithium based on solid electrolytes. The method comprises the following steps: mixtures containing lithium metal are used as anodes, and the solidelectrolytes containing lithium ions are used as electrolytes for electrolysis reaction in an electrolysis device to obtain the metal lithium on cathodes. The method can prepare high-purity metal lithium with coarse lithium as raw materials, so that the cost is prominently reduced; and meanwhile, the generation of chlorine in the anode reaction process can be prevented, so that the corrosion of the electrolysis device is prevented, and prominent advantages are achieved compared with such traditional methods as electrolysis melting of lithium chloride.