The present invention relates to: a method for concentrating a protein in a grain powder a protein-concentrated grain powder produced by the method and a feed additive containing the protein-concentrated grain powder. In the method for concentrating a protein in a grain powder according to an embodiment of the present invention, the grain powder is subjected to an enzymatic treatment to increase the soluble sugar content in the raw material, and the increased soluble sugars are removed through the inoculation of bacteria or yeast and a fermentation procedure, so that the protein can be concentrated to enhance the protein content fraction increase effect and improve the performance of the grain powder as a protein source.
