Seed propagation of exotic species, especially from remote floristic regions, contributes to their heterogeneity, which leads to the successful breeding of the species in specific environmental conditions; this method is the simplest and most cost-effective and contributes to a better adaptation of plants. To improve the efficiency of artificial selection to select the most promising genotypes it is necessary to study intra-individual variability of the seed progeny selected according to a number of signs. The aim of this work is the comparative analysis of the variability of Mongolian oak seedlings, grown from seed specimens, selected in the arboretum of the Siberian state technological University. The seeds of Mongolian oak have been planted in the arboretum of the Siberian state technological University in autumn 2012. At the end of the growing season of 2015 the account was made: we measured height, stem diameter at the root collar the number of leaves. As the result of the research it was found out that the average height of seedlings three was 32,2-37,5 cm with average coefficients of variation. The diameter of the inner barrel significant differences between families was not observed. The number of leaves was the best offspring of the family A-3. It can be concluded that seed progeny is characterized by significant variability, reflecting their genetic heterogeneity and can serve as the decision of the selection task to evaluate the direction of natural selection in certain environmental conditions. We select the most promising specimens for further reproduction, which differ in height, trunk diameter, and number of leaves. The calculated coefficients of heritability of height specify that in the seedlings which are grown up in uniform ecological conditions, the variability is caused first of all by a genotype.