Abstract: Alkaline hydrolysis process of potato dietary fiber was optimized by response surface methodology. The results showed that the optimum conditions for alkali modification of potato dietary fiber were as follows:treatment time was 40min, temperature was 83℃, alkali concentration was 0. 6% and solid-to-liquid ratio was 1:30. Under the optimum conditions, 17. 01% soluble dietary fiber was obtained, and yield of soluble dietary fiber was similar to predict value. After alkali modification, the swelling and water retention ability of soluble dietary fiber (SDF) were 11. 64mL/g and 3. 81g/g, respectively.