The invention discloses high-nutrition slowly digestible buckwheat powder. A preparation method of the buckwheat powder includes the specific steps: (1) mixing and homogenizing buckwheat powder and water to prepare starch milk; (2) adding protease for enzymolysis; (3) adding pH (potential of hydrogen) regulators for regulating pH and placing the starch milk into a boiling water bath for gelatinization; (4) cooling a gelatinization product to room temperature and then refrigerating and drying the gelatinization product to prepare the high-nutrition slowly digestible buckwheat powder. The high-nutrition slowly digestible buckwheat powder is high in polypeptide and slowly digestible starch content, allergen factors in buckwheat can be eliminated, blood glucose regulation capacity is enhanced, the nutritional value of the buckwheat can be increased, and the high-nutrition slowly digestible buckwheat powder can be applied to food additives and nutrient enhancers.