Abstract: Three types of callus，which present different regeneration capacity，were established in the tissue culture of strawberry．The Ⅱand Ⅲ types of callus possessed higher regeneration capacity while I type of callus had much lower．In the freshly induced calli，the Ⅱand Ⅲ types of callus had 5-fold and 9-fold higher contents of intracellular H₂0₂，and 3-fold and 4-fold higher level of 0₂^-.，compared with the I type of callus,respectively．Also，the calli Ⅱand Ⅲ had much higher activities of antioxidant enzymes than the callus I. During the subculture，H₂0₂level increased gradually and 0₂^-. rapidly，while the activities of antioxidant enzymes gradually declined．The ability of expression of totipotency in calli decreased，especially the callus I lost the ability after 12 week subculture．The results indicated that the reactive oxygen species might play a dual role in the regeneration of strawberry calli．On the one hand，a certain level of ROS may have a positive effect on the regeneration，and on the other hand，high level of ROS is inhibitory for the expression of totipotency in calli．

Key words: Strawberry, Reactive oxygen species, Antioxidant enzymes, Regeneration capacity, Callus