In model experiments in soil culture, the effect of various methods of applying sodium selenite on the formation of yield and amino acid composition of grain varieties of spring wheat Zlata and Ester, depending on water supply conditions, was studied. Sodium selenite was introduced by pre-sowing seed treatment and leaf treatment of vegetative plants. The study simulated optimal water supply conditions and soil moisture deficiency during the critical period of plant growth. The role of selenium in the regulation of the production process and the formation of the amino acid composition of spring wheat grain was studied. It was found that the production process of wheat plants, both under optimal water supply and in drought conditions, depended on the method of application of selenium and the varietal characteristics of spring wheat. The results allowed us to assume that selenium activated the attenuating ability of the ear by enhancing its acceptor properties. Under these conditions, the grains were better provided with assimilates. this made it possible to form the maximum possible yield of wheat grain. In conditions of drought, during leaf treatment of plants with sodium selenite, favorable conditions were created for the formation of reproductive organs of wheat, which stimulated the restoration of the processes of assimilate outflow from the vegetative mass into the forming grains. This made it possible to influence production processes and reduce the depression of wheat crop formation. The use of selenium revealed an increase in the total content of key amino acids, which had a significant effect on the antioxidant status of plants and contributed to the realization of their adaptive potential. The positive effect of selenium on the content of a number of amino acids, including on the assimilation of methionine, was revealed, which was probably due to the synthesis of selenomethionine, since the ways of their formation are similar and it is not possible to separate them. The greatest effect of selenium was observed in the cultivation of wheat of the Zlata variety compared with wheat of the Ester variety, which was determined by varietal differences inherent genetically and the unequal protein content in the grain.