On the territory of the Western Sayan mountains the new cenopopulation of rare species Fritillaria sonnikovae Schaulo et A. Erst was described. The objective of research was to examine the biology and characteristics of stability of cenopopulations. The geobotanical description of a plant association with participation of the studied sample was carried out by common method. Constructing the ontogenetic spectrum we relied on L.B. Zaugolnova’s ideas on the spectrum types. Ecological density was determined according to Yu. Odumu. The type of cenopopulation was established according to the classification by L.A. Zhivotovsky based on sharing of efficiency indexes (ω) and related age (∆). It was established that the rhythm of seasonal species development belonged to the group of early spring hemiephemeroids. At cenopopulation F. sonnikovae studying individuals of the type were detected only on five sample area, their ecological density reached 18. Cenopopulation F. sonnikovae invasion, young. Self-maintenance was generally carried out in the seed way.In an ontogenetic spectrum of cenopopulation the maximum was found in individuals of an immature ontogenetic state; the left-hand ontogenetic spectrum was formed. In general 86.7 % fell to the share of individuals of pregenerative fraction, 55.6 % made sprouts which most part was subject to elimination. Compliance characteristic and concrete ontogenetic spectrum showed a steady condition of a cenopopulation at the time of studying, however rather low share of generative individuals (the generative fraction made only 13.3 %) complicated forecasting its future development. Сenopopulation demands additional further studying in dynamics.