In the study,normal design of three factors and three levels was adopted according to the Box-benhnken central composite design method,using wheat bran as raw materials and extrusion technology.The content of soluble dietary fiber was used as the response value to study the Response Surface Methodology(RSM).The results showed that the optimum conditions for the extrusion modification were as follows: water ratio of raw material 23%,puffed temperature 133℃,rotation speed 225 r/min.Under the above conditions,the theoretical result of extrusion modification was 15.66% and the actual one was 15.42%.The relative error between them was 1.40%.