Abstract:This study investigated the effects of freeze-drying and powdering processes on the polysaccharide content，antioxidant activity，and fine powder quality of fresh Dendrobium officinale. The results showed that freeze-drying at -30 ℃ for 12 h after pre-freezing at -30 ℃ for 2 h was suitable for D. officinale segments. Under this condition，the polysaccharide content of freeze-dried D. officinale reached 4.78% （calculated based on fresh D. officinale），increased by nearly 49.5% compared to that of hot air-dried D. officinale. For the freezedried D. officinale，the IC50 values representing antioxidant activity were 2.356 mg/mL （DPPH radical），2.782 mg/mL （ABTS+ radical），2.108 mg/mL （superoxide anion radical），and 2.658 mg/mL （hydroxyl radical）. Passing through 80 mesh sieve，it afforded fine powder（55.46% of the total），which was bright with a blue-green color. The fine powder was easily dispersed in hot water above 75 ℃ with a clumping rate of less 5%. The viscosity of the brewing water reached 17.14 mm2/s，4.8 times that of hot air-dried D. officinale powder. When the freeze-dried D. officinale powder was brewed with hot water at 95 ℃， the polysaccharide content in the aqueous solution reached over 35%， which was about 16% higher than that when the powder of hot air-dried D. officinale was brewed.