Abstract: This study aimed to develop a medium-low glycemic index (GI) cereal meal replacement powder suitable for diabetic patients using selenium-enriched germinated brown rice, red adzuki beans, barley, tartary buckwheat, bean dregs, and mulberry leaf extracts as raw materials. The baking processing technology was optimized through response surface experiments using sensory scores and GI value-weighted scores as indicators. At the same time, the effects of the two processing methods of baking and extrusion on the microstructure, crystal properties, gelatinization properties, gelatinization degree, brewability, caking rate and other physicochemical properties of selenium-enriched germinated brown rice meal replacement powder were discussed. The results showed that the GI value was 62.75, the sensory score was 91.17, and the highest weighted comprehensive score was 60.69 under the optimal conditions of the baking time of 35 minutes, the baking temperature of 140 °C and the material-to-liquid ratio of 1:1 (L/kg). Compared with unprocessed meal replacement powder, the relative crystallinity of baked meal replacement powder and extruded meal replacement powder decreased to 15.15 and 4.28 respectively, and the B-type and V-type crystals increased. The round starch granules in the microstructure of the other two meal replacement powders were reduced and irregular granules were increased. In the electronic nose comprehensive evaluation equation, the comprehensive odor score from high to low is baked meal replacement powder > extruded meal replacement powder > unprocessed meal replacement powder. The experimental conclusion shows that the optimal GI value of baking meal replacement powder is between 55 and 70, which belongs to the medium-low GI range and is suitable for people with diabetes. It can be recommended as the preferred processing parameter for the development of meal replacement powder with a medium and low glycemic index.