The article objective is to define the biochemical composition of Leymus chinensis (Trin.) Tzvel., its nutritional and energy value in the southern steppe zone of eastern Transbaikalia, growing in different soil and environmental conditions due to the lack of such data. The authors use standard biochemical methods to determine nutrients calculated by assessing the nutritional value and energy of plant forage. Statistical data processing is carried out in Microsoft Excel. The paper examines content of crude protein, sugars, crude fat, crude cellulose, nitrogen-free extractives, feed units and metabolizable energy in dry matter of Leymus chinensis for the first time. The study ascertains a definite relation of the nutrient accumulation, and soil and environmental conditions, growing season duration, plant development phase, and the species adaptation to prolonged aridization, which causes its vegetative reproduction due to a decrease in generative reproduction. It reveals protein ratios as an indicator of forage digestibility. The research found that the amount of both digestible nutrients, and the content of energy and metabolic energy in the forage varied in a rather narrow range, which is associated with the short growing season of Leymus chinensis development under the harsh continental climate of the steppe zone in eastern Transbaikalia.