Abstract: Using highland barley, mung bean, black bean and Tartary buckwheat as raw materials, the multigrain meal replacement powder was set by twin-screw extrudation technology. The changes of nutrient composition, volatile flavor, crystal structure and other physicochemical properties were tested before and after extrudation. The results showed that the contents of protein, fat, moisture, starch, total phenol and total flavone of multigrain meal replacement powder were reduced by 2.83%, 0.47%, 4.45%, 2.62%, 17.89 mg/100 g and 9.02 mg/100 g, respectively. The changes of dietary fiber and ash were not significant. The aldehydes, alcohol and heterocyclic substances that contribute more to the flavor were increased, which greatly improved the flavor. The crystal structure changed from A-type to V-type, and the crystallinity reduced by 24.97%. RVA and DSC results showed that the peak viscosity, minimum viscosity, disintegration value, final viscosity, recovery value and peak time decreased by 156, 46, 110, 111, 177 cP and 2.2 min, respectively. The enthalpy change decreased to 0.15 J·g⁻¹, indicating that most of the starch had been gelatinized. The results of gel texture showed that the hardness and adhesion decreased by 35.72 g and 4.08 g respectively, while the adhesion, cohesiveness, elasticity and capability increased by 5.11 g, 0.19 Ratio, 5.08 mm and 1.98 mJ respectively, giving it a good taste. The study of the quality characteristics of the powder showed that the content of soluble solid and the water holding capacity increased while the oil holding capacity decreased. The characteristics of power were obviously improved. The color changed obviously.