The invention relates to a solid-phase decarburization method of high-carbon Fe-Mn alloy, and the method aims at the actual situation that the carbon content of Fe-Mn alloy powder is high and adopts the solid-phase decarburization technology. The method comprises the following steps: by using calcium carbonate powder as decarbonizer and nitrogen as protective gas for decarburization, decarburization is performed in a microwave decarbonization furnace, wherein the temperature of microwave heating is 1000 DEG C, the heating time is 60min, the specific power of microwave heating is 10KW/kg and the rate of decarburization is up to 85.78%; and the obtained low and medium carbon Fe-Mn alloy is briquetted by a briquetting machine to prepare a block material for use, wherein the calcium oxide in the material is a good desulfurization and dephosphorization agent, and the generated carbon monoxide gas can be recycled. The method does not discharge metallurgical residue and cause the pollutions caused by waste gas, wastewater and residue, is a clean decarburization technology and is an ideal solid-phase decarburization method of high-carbon Fe-Mn alloy.