Abstract: To address the issues of poor nutritive properties, dispersibility, and stability associated with grain meal replacement powders produced using traditional methods, the present study investigated the ultrafine grinding of sprouted brown rice for different durations ranging from 5~20 min, the aim was to examine the effects of ultrafine grinding on the physicochemical characteristics of the powders, including particle size, essential nutrients, bioactive compositions, dispersibility, pasting characteristics, crystalline structure, and thermal properties. The results indicated that the ultrafine grinding treatment enhanced the solubility of key nutrients such as protein, starch, fat, and dietary fiber, as well as primary bioactive components including γ-aminobutyric acid, total phenols, total flavonoids, and γ-oryzanol. Notably, the powder's color homogeneity improved, the crystallinity of starch decreased from 28.41% to 20.86%, accompanied by a reduction in short-range ordering, the water-solubility index improved by 12.82% and solubility increased. Meanwhile, the regrowth value decreased to 26.67 cP, and the disintegration value was reduced to 206.33 cP. Additionally, the enthalpy change of pasting (∆H), packing density, and vibrational density were significantly reduced (P<0.05). The highest sensory score of brown rice micronutrient powder was obtained at 10 min duration of ultrafine grinding. In conclusion, ultrafine grinding technology can effectively enhance the dissolution of nutrients in brown rice flour, improve its physicochemical properties, increase the aging resistance of starch, and enhance processing suitability, thereby providing valuable scientific insights for the comprehensive development and utilization of brown rice flour.