The invention discloses a method for concentrating germanium in low-grade germanium concentrate by thermal reduction volatilization, belongs to a germanium extracting method in the technical field of metallurgy and particularly relates to a method for concentrating the germanium in the low-grade germanium concentrate by the thermal reduction volatilization. The method for concentrating the germanium in the low-grade germanium concentrate by the thermal reduction volatilization comprises the following steps of by taking sodium hypophosphite as a reducing agent, uniformly mixing the low-grade germanium concentrate with the sodium hypophosphite, and placing the mixture into a reducing volatile furnace; after the reducing volatile furnace is isolated from air, performing reducing volatilization by adopting a microwave heating mode under the condition of 900 to 1,100DEG C, wherein the germanium in the low-grade germanium concentrate volatilizes in a form of germanium monoxide and enters a dust collecting cloth bag, so that the germanium is separated from a large amount of other non-volatile impurity components; collecting volatile matters to obtain germanium concentrate with high content of germanium; oxidizing the germanium concentrate with high content of germanium in hydrochlric solution with manganese dioxide; leaching hydrochloric acid by heating, and then performing distilled water separation to extract the germanium. The method has the advantages of higher germanium recovery rate, lower production cost and less equipment input; the discharge and the treatment of a large amount of waste water, waste gases and waste residue are avoided; the problem that waste acid, the waste water and the waste residue are difficult to treat due to wet process treatment can be thoroughly solved; the pollution to the environment caused by the germanium extraction process can be greatly reduced.