Abstract:This study took Dendrobium officinale as the research object and used different doses of 60Co-γ ray irradiation for one-time treatment（1，2，5，10，15 kGy，and 25 kGy）and two irradiation treatments at the same dose.The aerobic plate count，crude polysaccharides，total flavonoids，mannose，and other substances in Dendrobium officinale before and after irradiation，as well as their DPPH free radical scavenging ability，were compared to determine the safe dose for irradiation sterilization of Dendrobium officinale.The results showed that a radiation dose above 10 kGy could completely kill the microorganisms in Dendrobium officinale.With prolonged storage time，the residual radiation gradually decreased，and after 90 days，the photostimulated luminescence（PSL）value screening result of Dendrobium officinale after irradiation was negative.At radiation doses of 10 kGy and 15 kGy，the contents of crude polysaccharides，total flavonoids，mannose，and the DPPH free radical scavenging ability of the ethanol extract in Dendrobium officinale were not affected.Compared with the blank sample，the contents and in vitro activity of various indicators increased.However，after one-time irradiation at a dose of 25 kGy or two irradiations at doses of 10，15 kGy，or 25 kGy，the contents of active components of Dendrobium officinale decreased compared with the first irradiation，and the DPPH free radical scavenging ability of the ethanol extract decreased.Based on the changes in various indicators，the safe dose of 60Co-γ ray irradiation for Dendrobium officinale was 10 kGy，and the contents of active components and antioxidant activity increased.Two irradiations at the same dose or high-dose irradiation reduced the contents of active components and antioxidant activity of Dendrobium officinale，but there was no significant change in its protein content，which may be related to the protein detection method.