Extrusion is an effective technology to increasing the contents of soluble dietary fibers (SDF). Response surface methodology (RSM) was applied to optimize operational parameters of extrusion. The determination coefficient (R2) was 0.80, and the results show that the regression models could explain the data variation and represent the actual relationships between the parameters and responses. The optimal operational parameters were: ratio of water 28%, zone temperature119.7 °C and rotation rate of screw 159.0 r/min. Under the optimal conditions, the maximum yield of SDF of 0.078 g/g in theory and 0.076 g/g in the experiment were obtained, with an increase of 15.1 % compared to the original yield (0.066 g/g) without extrusion process.