The effect of elevated levels of UV-β radiation in the vegetation experiment was studied. The object of the study was barley Zazersky 85 varieties, changes in the content of ascorbic acid and glutathione were revealed. It is known that even a small increase in the intensity of UV-β radiation can have a significant impact on the plant growth, development, photosynthetic and biochemical reactions. UV rays induce various DNA damage, and also contribute to the formation of free radicals in cells that cause lipid peroxidation of biological membranes. The existence of a plant cell in oxidizing conditions is possible only through the development of antioxidant defense mechanisms system. Particular attention is paid in this regard to ascorbic acid - vitamin C and glutathione. Ascorbic acid and glutathione are not considered separately, but as a redox pair to ensure the redox tone of the cell. In some reactions they can act independently of each other participating in a signaling system to transmit information in response to stress. Plants were grown in vessels containing 4.5 kg of air-dry soil. The repetition is sixfold (six vessels in each variant). As a source of UV-β irradiation were used LER-40 luminescent erythemal lamps (Russia). Plants were irradiated from the seedling stage to full ripeness from 10 to 14 h. Additional to solar UV-β irradiation levels are expressed in terms of the daily biologically effective dose taking into account the generalized spectrum of action for higher plants. The differences in the activity of oxidative processes and antioxidant protection depending on the stress degree have been established. The dose-dependent UV-β irradiation increase in the MDA content in the leaves indicates a pronounced oxidative stress due to a decrease in the efficiency of the photoreactivation process and the repair of DNA damage, which is caused by the partial shielding of the low-intensity UV radiation of area A in the greenhouse, which resulted in a decrease in biomass.