Abstract: The present application relates to the technical field of further processing of dairy products, and in particular to a preparation method of milk oligosaccharides, and milk oligosaccharide powder and food prepared thereby. The preparation method comprises the steps of: performing ultrafiltration of whey liquid for at least three times, subjecting the ultrafiltration permeate to nanofiltration concentration for several times, then subjecting the nanofiltration retentate to chromatographic separation and purification, collecting chromatographic collection liquid containing sialyllactose while removing the fraction containing lactose, subjecting the collection to desalination and drying to obtain oligosaccharide powder. The milk oligosaccharides prepared by the present method and the food product containing the same comprise basically bovine milk oligosaccharides, which are light yellow or white in color, light in flavor, uniform in size, and have good thermal stability and solubility.