The The Poti River Canyon State Park (24,772.23 ha), located in the municipality of Buriti dos Montes, is an important Conservation and Environmental Protection Unity in the State of Piauí. Therefore, this research purpose was to identify the angiosperms species which occurr in rocky outcrops in the aforementioned Park. The collection, herborization, identification and classification of specimens was followed the usual specialized literature. The specimens are deposited in the Herbarium Prof. Aylthon Brandão Joly, located on the Center for Superior Studies of Caxias, CESC / UEMA. The park's angiosperm flora is composed by the 96 species, distributed in 82 genera and 34 families. Among these, 85.4% (82 spp.) are eudicotiledonous and 14.6% (14 spp.) are monocotyledonous. The richest families in number of species were Fabaceae (21 spp.), Apocynaceae and Cactaceae (6 spp.); Bignoniaceae and Euphorbiaceae (5spp); Araceae, Anarcadiaceae, Boraginaceae, Cyperaceae and Malvaceae (4 spp.); Bromeliaceae and Rubiaceae (3 spp.), which together had a total of 71.9% of the species, while the others presented between one and two species (28.1%). For this study area, 8.3% (8 spp.) was the firts records for Piauí state, they are Astrocaryum vulgare Mart., Cyperus pohlii (Ness) Steud., Cryptostegia madagascariensis Bojer, Cordia oncocalyx Allemão, Ibatia ganglinosa (Vell.) Morillo, Piptadenia retusa P.G.Ribeiro, Seigler & Ebinger, Vitex gardneriana Schaue e Waltheria operculata Rose as its representants. 14,6% (14 spp.) are endemic to the Caatinga and 5,2% (5 spp.) are new species records for it. This is the first floristic study for the municipality, which contributes with important information to the area of rocky outcrops, increasing the occurrence and the geographic distribution of the species in Brazil.