The optimum process of extracting anthocyanin was studied based on single factor experiment with purple sweet potato residue as raw material to study the color-protecting techniques. On the basis of this, the best combination of the beverage was prepared with the taste, color and flavor as indexes. The result showed that the optimum condition for protecting color was 0.05% citric acid. The optimum technique of extracting anthocyanin was 1.0% citric acid with 50% ethanol as solvent, ratio of solid to liquid 1∶30, 75℃ water bathed for 1.5h, anthocyanin content in the extract was 0.1701g/100mL. The optimum formula of the beverage was that the extract of anthocyanins from purple sweet potato residue was 70 mL, the extract of Momordica grosvenori with relative sweetness of 22.55 was 30mL, sucrose 6g/100mL. It tastes a bit sweet and sour, with bright purple color and the light aroma of purple potato and Momordica grosvenori. The anthocyanin content in the product was 0.2194g/100mL, and the relative sweetness was 11.76. The color and the taste of the beverage were stable during the shelf life test (equivalent to one year), and the microbiological index was in accordance with the national hygienic standard for beverage products.