Materials of low-glycemic-index mixing powder were screened, on this basis, the formula of low-glycemic-index mixing powder was designed. Then, the effects of different processing methods (steaming, extruding and roller-drying) on expected glycemic index (eGI) and the solubility index (drying-matter solubility index, DSI) were investigated and the optimal processing method and parameters were obtained. Finally, the in vivo glycemic response to mixing powder was measured. The results showed that after cooking, extrusion, or roller-drying, oats, chickpeas, and bean had lower eGI. The optimal ratio of oat∶ chickpea∶ colored kidney bean was 16.43∶76.35∶7.22 in the mixing powder. The mixing powder with high DSI (16.45%) and low eGI (57.41) was achieved using extruding with terminal barrel temperature procedure of 60℃-80℃-100℃-120℃, water content of 25%, and screw speed of 100r/min. When glucose was regarded as 100, the glycemic index (GI) of mixing power was 52.13, suggesting the mixing powder belonged to low-GI foods.