Abstract: In this paper,the effects of twin-screw extrusion on the physical and chemical properties of barley flour were studied. Results showed that:Under the optimized process conditions(screw speed of 45 Hz,feed speed of 35 Hz,sleeve temperature of 140 ℃,raw material moisture content of 20%),the moisture contents,total starch contents,crude fat contents and protein contents of the extruded puffed flour decreased by 12.16%,6.89%,1.46% and 1.38%,respectively,compared with these before extrusion. The water absorption index and water solubility index increased 341% and 7.98% respectively,moreover,the color was deepened. The peak viscosity,the lowest viscosity,the final viscosity and the retrogradation value decreased by 3932.99,3036.93,5244.09 and 2206.81 cp respectively,and the gelatinization temperature decreased from 69.59 ℃ to 50.21 ℃ without obvious gelatinization process. Scanning electron microscopy showed that the starch granules of the extruded whole barley flour changed significantly,and all the materials were uniformly aggregated together,and showed a flake-like structure.