The study aimed to establish floral composition, diversity levels, category size, phytosociological structure, commercial use and ecological group of species present in the regeneration of open ombrophile forest in southern Amazon, Brazil. Data were collected at S?o Nicolau farm, in the municipality of Cotrigua?u, northwest of Mato Grosso state, coordinates 51°9'19.5"S and 58°14'53"W. One hundred plots of 10 × 10 m were allocated. All individuals between 29.9 and 59.9 cm had circumference at breast height (CAP) measure, with sub-plots of 5 × 5 m which were measured in all subjects between 1:50 m in height 29.9 cm CAP and sub-plots of 2 × 2 m for individuals between 0.30 to 1.5 m tall. The information obtained in the field were processed in excel spreadsheet. The results showed the occurrence of 610 individuals belonging to 82 species, 34 plant families, with a diversity index of Shannon & Weaver’s 2.77. The index of value of importance showed species Protium robustum, Maquira calophilla and Inga fagifolium with greater ecological importance in fitocenose. The higher values for Natural Regeneration were the species Protium robustum, Maquira calophilla and Inga fagifolium with 16.42, 8.03 and 7.76 respectively.