Provided are a method and molten salt system for recovering rare earth elements from NdFeB waste and use of ferric oxide as a raw material of a manganese-zinc ferrite. The molten salt system comprising the following components in percentage by weight: 40% of K3AlF6 or Na3AlF6, 40% of KBe2F5, and 20% of KAlF4. By adopting the three-component molten salt system of the present invention, recovery rates of rare earth elements extracted from NdFeB waste all can reach 98% or above. By adopting the three-component molten salt system, extraction temperature is 100-400° C. lower than that of all current similar halogenation methods, and extraction time is fold shorted to 1-3 h. The reduction of the extraction temperature and the shortening of the melting time greatly reduce the energy consumption of extracting rare earth elements from NdFeB waste, and the economic benefits are remarkable.