Abstract: This study examined how particle size affects the microstructure, physicochemical properties, antioxidant activity, and in vitro digestion of Dejiang Gastrodia elata powder using principal component analysis (PCA) to identify the optimal grind size, leaving its molecular structure unaffected. Dejiang G. elata was ultrafinely ground into four powdered fractions (50, 100, 200, and 300 mesh). The angle of repose and slip angle of the powder increased with decreasing particle size, whereas the bulk density, water-holding capacity, and oil-holding capacity decreased. The 200-mesh powder exhibited significantly higher soluble sugar content (13.43%) than the other particle sizes (P<0.05). Although no significant differences in polyphenol content were observed across particle sizes (P>0.05), the 50-mesh powder showed notably higher flavonoid (4.51%) and vitamin C (4.50 mg/100 g) contents (P<0.05), and the 100-mesh powder showed notably higher antioxidant capacity (P<0.05). During in vitro simulated gastrointestinal digestion, the 200-mesh powder exhibited significantly higher soluble sugar release, whereas the 300-mesh powder showed greater polyphenol release than the other particle sizes (P<0.05). Collectively, PCA identified 50-mesh as the optimal particle size for Dejiang G. elata powder, which provides a reference basis for further in-depth research on G. elata powder.