Beijing chrysanthemum was used to fabricate chrysanthemum micro-powders of different particle sizes via ultrafine grinding and sieving, and their physicochemical properties, nutritional components, and antioxidant activities were compared. The results indicated that the average particle sizes of the four chrysanthemum micro-powders with different particle sizes were 104.37, 74.84, 50.92, and 55.73 μm, respectively. As particle size decreased, the degree of fragmentation increased; the powder distribution of M80-M300 became more homogeneous, and the absolute value of the zeta potential decreased. However, when the particle size was M400, the chrysanthemum micro-powder underwent agglomeration and exhibited a non-homogenous distribution, with a new functional group appearing at wave number 2 364.5 cm-1. Differences in the swelling potential and water-holding capacity between M300 and M200 were not significant, increasing by 1.00 and 0.83 g/g compared with those of M18, respectively. M400 showed the highest solubility and oil-holding capacity at 36.17% and 1.55 g/g, respectively. The contents of soluble proteins, polysaccharides, total flavonoids, total phenols, characteristic monophenols, and amino acids as well as the antioxidant activity increased with decreasing particle sizes. The total phenolic and luteoloside contents of M300 increased by 0.38 g/100 g and 0.14 g/100 g, respectively, compared with those of M400 (P˃0.05); The total flavonoid content and DPPH free radical scavenging rate of M300 increased significantly by 2.41 g/100 g and 3.6%, respectively, compared to those of M400 (P<0.05). The polysaccharide content and essential amino acid ratio of M400 increased sharply by 2.88 g/100 g and 1.47%, respectively, compared with those of M300 (P<0.05). These results suggest that ultrafine grinding significantly improved the structure, nutrient release, and functional properties of chrysanthemum powders, and M300 may be suitable for further processing and utilization because of its higher overall performance.