The invention provides a gluten-free protein biscuit manufactured by sweet potato coarse dietary fibers and a preparation method of the gluten-free protein biscuit. Raw materials for manufacturing the gluten-free protein biscuit include sweet potato coarse dietary fiber starchy flour, sweet potato coarse dietary fiber superfine powder, sweet potato coarse dietary fiber nano-powder, sweet potato modified starch, extrusion sweet potato coarse dietary fiber powder, sweet potato coarse dietary fiber microwave treatment powder, sweet potato starch, food gum, plant source polyphenol, albumen, sugar, salt, baking soda, ammonium bicarbonate, edible oil, water and the like. The weight ratio of the raw materials is 10-40: 10-40: 10-20: 4-12: 5-12: 5-13: 0.5-6: 0.1-3: 0.1-0.7: 1-3: 0.5-25: 0.1-3: 0.1-1: 0.1-0.5: 14-34: 20-69. The sweet potato coarse dietary fiber gluten-free protein biscuit manufactured by the method has unique flavor of a sweet potato, is crisp in taste, golden in color and rich in protein, coarse fibers, vitamin, mineral elements and the like, and has fine nutrition and health care functions.