Abstract: Abstract: Osmunda japonica Thunb is an important source of edible plants in China and is also an important export earner. In order to study the effect of ultrafine grinding methods on Osmunda japonica Thunb's physical properties, main component contents and retention of active substances, planetary ball milling method and high-pressure homogenization method were used to ultrafine grinding. Ball mill material tank was added with the conventionally crushed Osmunda japonica Thunb sample of 10 g and corundum ball with mass of 100 g and diameter of 9 mm; ratio of ball mass to material mass was 10: 1, and rotation speed was 500 r/min. Crushing time was 1 h, and the resulting Osmunda japonica Thunb powder passed through 200-mesh sieve and then was placed in the dryer for spare. For the treatment of high-pressure homogenization, 16 g powder was accurately weighed after conventional treatment, and water was added to make the mass concentration lower; after colloid mill processed 10 min, and material circulation of Osmunda japonica Thunb was conducted 13 times, the high-pressure homogenization was performed. The homogenization pressure was 25 MPa and the time was 15 min. The inlet temperature of spray drying was 190 ℃, the outlet air temperature was 80 ℃, the feeding rate was 12.5 mL/min and the feeding temperature was 60 ℃. The superfine grinding powder's particle size, angle of repose, powder expansive force, holding water and oil force, and other physical properties were analyzed, and the total protein, crude fat, polysaccharides, total flavonoids, total polyphenols and other major components were detected. The hypoglycemic activity of 2 kinds of Osmunda japonica Thunb superfine powder was preliminarily investigated according to the inhibition ability of the extract of Osmunda japonica Thunb to α-glucosidase and α-amylase. The results showed that due to the treatment of planetary ball milling method and high-pressure homogenization, the particle size of the powder decreased by 48 and 65 times, respectively. Scanning electron micrograph observation of the ultrastructure of Osmunda japonica Thunb after ultrafine pulverization revealed that most of the fiber structure was destroyed, the particle size was more uniform, the specific surface area of the powder increased, and the angle of repose was slightly larger than that of the conventional powder. Osmunda's power expansive force decreased significantly, and water solubility increased, indicating that after ultrafine pulverization, long chain cellulose significantly reduced and short chain increased, resulting in the lower bound force on water and the decreased powder expansive force. And this change in physical properties is conducive to the exposure of water-soluble components and they are easier to be fully dissolved, and high-pressure homogenization in the higher temperature makes the powder group more exposed to improve the water solubility. The change of physical properties of the superfine pulverized Osmunda japonica Thunb powder helps to improve the processing properties of the Osmunda foods and produce the high value-added products. The main component contents from high to low were high-pressure homogenization crushing > planetary ball milling > conventional crushing. The inhibition ability to α-glucosidase and α-amylase from high to low was high-pressure homogenization crushing > planetary ball milling > conventional crushing. The above results show that both methods of ultrafine grinding have an effect on improving the physical properties of the powder, and the fiber tissue of the Osmunda powder is destructed more completely by the high-pressure homogenization, and main components are easier to be eluted. The micropowder treatment promotes the hypoglycemic physiological function of the powder.