The wheat bran was used as raw material and alkali was the catalyst in the study. The processing conditions of extrusion modified wheat bran and it's impacts on wheat bran main components was studied. The results indicated that the main influence factor on extrusion modified wheat bran was the alkali concentration,then the extrusion temperature and material moisture,the least one was the rotate speed. The optimum processing conditions were:sodium hydroxide as the catalyst,particle size 60 mesh,32.5% moisture,4.5% (calculated by moisture content of materials) of alkali concentration,temperature 115 ℃ and rotating speed 250r/min. Compared with no alkali one,the contents of fats and proteins were almost no change. However,the starch,IDF and phytic acid content decreased by 18.34%,39.76%,72.87% respectively. The SDF increased by 96.72%.