The identity of the highland vegetation of the eastern part of the ridge East Sayan is due to the history of the formation of flora and vegetation in the late Pleistocene, as well as to the features of underlying rocks, mainly represented by limestones. As a result, endemic plant species and communities formed on these ancient alignment surfaces. One of these species is Festuca komarovii Krivot. (Komarov fescue). The relictness of Festuca komarovii is confirmed by the systematic position of the species in the generic complex; it belongs to the distinctive section Leocopoa (Griseb.) Krivot. The section combines only three species – Festuca sibirica, F. hubsugulica, F. komarovii, of which the last two are endemic of the Hangai-Sayan center. The Komarov fescue in the modern vegetation of the East Sayan shows itself as a coenogen and indicator of paleocryogenic landscapes. The research results showed a high coenotic role of this fescue in the vegetation of the studied territory, in particular the syntaxa of the cryophyte-steppe florocenotype (unions Kobresion myosuroidis Mirkin et al. 1983 em. Hilbig 2000 and Potentillo niveae–Caricion pediformisТеlyatnikov 2011). We also described the new association Ptilagrosto mongholicae–Festucetum komarovii Namzalov ass. hoc loco, floristically and coenotically related to the associations of the union Dryadion oxyodontae Zhitlukhina et Onishchenko ex Chytrý et al. 1993, which belongs to the class Carici rupestris–Kobresietea bellardii Ohba 1974. However, one important feature should be noted that the Komarov fescue in communities of associations of tundra and subalpine forest vegetation is noted in a small abundance as an accompanying species. To some extent, this confirms the initial coenogenetic proximity of Festuca komarovii to grass ecosystems – cryophytic stepoids of the periglacial Pleistocene complex.