Species composition of the moss flora of limestone outcrops in Serga River valley (Deer Springs Natural Park) has been studied and analyzed for the first time. In this work we have revealed 103 species and 1 variety of mosses from 67 genera and 29 families. Precise taxonomical, geographical and ecological flora's analysis has been processed. We indicated Encalypta trachymitria and Fissidens osmundoides for the Middle Urals for the first time. 33 rare species have been shown, and five from them (Encalypta trachymitria, Fissidens bryoides, Hymenostylium recurvirostrum, Timmia austriaca, and Tortella alpicola) are recommended for inclusion in the Red Book of Sverdlovsk Region.