The invention discloses a dairy cow fermented feed. According to the dairy cow fermented feed, terrestrial alkaline plant resource froggrass is adopted as a raw material, microbial fermentation is used to produce the dairy cow fermented feed which has high content of protein and strong palatability, and is rich in probiotics of brewer's yeast, bacillus subtilis and the like, high-valued utilization of saline and alkaline terrestrial plant resource froggrass is achieved, and the disadvantage that dairy cow protein feed is scanty is solved. According to the dairy cow fermented feed, the froggrass is used as the raw material, seaweed residues, lucerne meal, straw, Chinese herbal medicine and the like are supplemented, and the dairy cow fermented feed is prepared through a technology of two-stage fermentation of a biological leavening agent; the dairy cow fermented feed is rich in probiotics of saccharomycetes, aspergillus niger, bacillus subtilis, brewer's yeast, lactic acid bacteria and the like, the content of the probiotics reaches up to 2-5*10<8>cfu / g, after the dairy cow fermented feed is used in cow breeding, immunity of the organism of a dairy cow can be remarkably improved, growth of the dairy cow can be promoted, milk yield can be increased, milk quality can be improved, and the dairy cow fermented feed has very high application and popularization value.