[Objective] To examine the effects of saponin on the metabolism of reactive oxygen species (ROS), the activities and the gene expressions of superoxide dismutase (SOD) and catalase (CAT) in Hypsizygus marmoreus mycelium. [Methods] Hypsizygus marmoreus mycelium were treated with 0, 0.01, 0.05 g/L saponin for 7 to 15 days under shake-flask culture condition. [Results] The content of superoxide radical and MDA increased than the control group during 7 to 11 days adding saponin to the culture, and then decreased than the control group after 13 days. SOD activities enhanced with the increasing of saponin concentration during 7 to 15 days (except the 9th day), especially during 13 to 15 days. CAT activities showed the same trends as SOD activities, and always kept a high level with 0.05 g/L saponin exposure. The abundance of Mn-SOD and CAT genes were up-regulated in all concentration treatments. With 0.05 g/L treatment, the expression of gene encoding Mn-SOD showed the same trend as SOD activities. However, expression of CAT gene was not in accordance with the trend of CAT activities. It inferred that CAT activities might effected by post-translational modification. [Conclusion] Saponin can induce the increase of antioxidant enzyme activities of SOD and CAT, as well as up-regulate corresponding gene expressions, which might slow down the accumulation of MDA and superoxide radical in the later culture period.