The invention relates to molybdenum-tungsten-iron alloy and a preparation method thereof, and belongs to the technical field of mineral extractive metallurgy. The preparation method of molybdenum-tungsten-iron alloy comprises the following steps: adding the following raw materials such as calcium oxide, molybdenum and tungsten mixed crude concentrate, silicon iron and scrap iron into a crucible in sequence, rising the temperature to 400-600 DEG C, performing heat preservation for 3-5 min, continuously rising the temperature to 1500-1700 DEG C, performing heat preservation again for 1-3 min, and cooling, so as to obtain the molybdenum-tungsten-iron alloy. According to the preparation method of molybdenum-tungsten-iron alloy provided by the invention, molybdenum and tungsten mixed crude concentrate, calcium oxide, silicon iron and scrap iron are taken as the raw materials, the process is simple, and the required smelting time is as short as 1-3 min; compared with other methods, the preparation method has the advantages that the separation and purification processes of molybdenum and tungsten mixed crude concentrate are avoided, the smelting time is greatly reduced, the production cost is reduced, the resource utilization ratio is improved, and economic benefits are increased.