Studying of plant vegetation is a prelude to many researches and executive projects. Herbaria are permanent treasures of plant specimens for a region and the best source of information about the flora of the region. The present study is concerned with the identification of plant species of herbarium of Damghan University (DU, Semnan province). Based on the results obtained from the plant identification of herbarium specimens, a total of 311 species belonging to 237 genera and 68 families from Semnan province were identified. The most species richness families were Poaceae (23 genera, 32 species), Asteraceae (23 genera, 30 species), Lamiaceae (16 genera, 24 species), respectively. Also, the genus Bromus with 6 species, Salsola, Stachys and Prunus each with 5 species and Chenopodium with 4 species are the largest genera in the region. This study documents 122 medicinal and 8 halophytic plant species in the region. Moreover, 25 plant species were listed as threatened species based on the criteria of the International Union for Conservation of Nature.