Résumé : The Fina Reserve is subject to human and pastoral disturbances. These disturbances seem to be generalized. Entirely protected areas no longer escape. This study proposes itself to provide the characteristics of the natural vegetation mainly ligneous in the areas which are not yet disturbed in this reserve. Homogenous units not yet disturbed in comparative ecological conditions have been identified in the central area fully protected. Eighteen samples of 2 500 m2 have been collected in these units. The application of the factorial analysis of the corresponding on the collected matrixes per ligneous species has helped identify four plants groups defined according to the topographic or toposequence position of the units (tray, valley, glaze and plain). The flora identified during the study, mainly composed of phanerophytes comprises 89 species grouped into 58 types and 29 families. The three species mostly common are Combretum glutinosum, Acacia macrostachya, Anogeissus leiocarpus. The associative group on the glacis has higher specific riches and a more important coverage. But, the earthy surface is more important at the level of the tray and increase in accordance with the density.