The invention relates to a food grade lubricating grease used for feed processing machines, and a preparation method and an application thereof. The lubricating grease comprises, by mass, 85-95% of base oil, 5-15% of a composite aluminum thickener, and 6-12% of an additional extreme pressure anti-wear agent. The preparation method comprises the following steps: heating all the base oil to 50-60 DEG C, adding benzoic acid, heating benzoic acid to 70-80 DEG C, adding a preheated aluminum stearate polyoxide polymer after the benzoic acid is dissolved, stirring the dissolved benzoic acid and the preheated aluminum stearate polyoxide polymer, heating the stirred materials to 150 DEG C in 1-2 h, continuously heating the stirred materials to a highest refining temperature of 200-220 DEG C, cooling the heated materials to 80 DEG C, adding a pressurizing anti-wear agent, uniformly stirring all above materials, grinding the obtained mixture, degassing the ground mixture, and filling the degassed mixture. The preparation method of the lubricating grease has the advantages of simplicity, short cycle, and improvement of the quality of the above product and the safety and the healthiness of the production process only through three raw materials. The lubricating grease meets lubricating demands in running of the feed processing machines, such as granulator devices, and accords with the safety and health demands in the feed processing industry.