Objective: This work was aimed to analysis the influence of steaming processing on the extraction， physiochemical properties， and digestion properties of sweet potato soluble dietary fiber(SDF). Methods: The response surface methodology and desirability function were conducted to optimize the solid-liquid ratio， extract temperature， and extract time of sweet potato SDF extraction for higher yield and total sugar content. SDF from steamed sweet potato (SDF-S) and from fresh sweet potato (SDF-F) were extracted by the optimized parameters. The yield， polysaccharide composition， and dietary fiber content， as well as water holding capability and oil holding capability， were measured to compare the differences of two SDF. Besides， simulated digestion in vitro was performed to assess the digestion properties. Results: The optimized parameters were 1∶16 of solid-liquid ration， 40 ℃ of extraction temperature， and 40 min extraction time. The SDF-S showed significantly higher yield [(6.13±0.25%) vs (2.89±0.18)%]， neutral polysaccharide content [(59.31±0.73)% vs(46.83±0.63)%]， acidic polysaccharide content [(25.36±0.48)% vs (9.60±0.14)%]， dietary fiber content [(54.71±6.70)% vs (35.69±3.25)%]， water holding capability [(4.60±0.31) g/g vs (3.27±0.21) g/g] and oil holding capability [(3.30±0.40) g/g vs (1.82±0.28) g/g] than SDF-F (P＜0.05)， while the SDF-F showed better resistance to digestion than SDF-S. Conclusion: Steaming processing improved the accessibility of sweet potato SDF but weakened its resistance to digestion.