The invention discloses a method for preparing buckwheat protein concentrate rich in polyphenols. The preparation method comprises the steps of taking tartary buckwheat cortex flour as a raw material and performing homogeneous dispersion pretreatment; sequentially utilizing alpha-amylase and glucoamylase to perform enzymolysis on the tartary buckwheat cortex flour; utilizing a membrane separation method to effectively remove micromolecule impurities in feed liquid, and obtaining the buckwheat protein concentrate rich in polyphenols after freeze drying. The protein extraction rate of the product is 57.93%, the total polyphenol content is 11.35%, and the protein extraction rate and the total polyphenol content are higher than those of a conventional alkali dissolution acid settlement method. The method is simple and feasible in process and short in time and can be applied to developing special proteins having special functions (such as blood fat reduction and blood pressure reduction) and relevant products.