Antioxidant enzyme activities and malondialdehyde(MDA) content of two barley cultivars,Yerong(waterlogging-tolerant) and Franklin(waterlogging-sensitive) were studied with a field experiment under control and waterlogging stress.Waterlogging stress altered MDA content and the activities of superoxide dismutase(SOD),peroxidase(POD) and catalase(CAT) in barley leaves.In general,increase of SOD and POD induced by waterlogging were found at early stage of waterlogging stress,however,SOD activity of Franklin began to decrease with prolongation of waterlogging time.The changes of CAT activity were inconsistent under waterlogging stress in the two barley cultivars.MDA content increased in both tolerant and sensitive genotypes under waterlogging stress,while Franklin accumulated much more MDA than Yerong did.It was concluded that higher SOD activity and less MDA content may be involved in waterlogging tolerance of Yerong,and the results above indicated that MDA content,SOD and POD activity could be used as the physiological indicator of tolerance to waterlogging in barley.