This work is the result of a floristic study conducted in the various strata of dense forests of the Masako Forest Reserve. It aimed to identify and compare the riclU1ess of each stratum in the two forest types, to analyze the relationship between strata and finally to estimate the parameters of stand structure (density, basal area, dominant height and structure diametric trees). The inventory method in making full use of measures of dbh (dbh ::: 10 cm) and the method of multi-layered phytosociological records (list synusial) were used to inventory the trees on land. A total area of six hectares has been established in the undisturbed forest reserve of Masako, three acres subdivided into 12 plots of 2,500 m2 each were installed in the primary forest to monodominant Gilbertiodendron dewevrei and three hectares subdivided in 12 plots of 2500m 2 eachinstalled in the old secondary forest. The two methods chosen have identified an overall total of 2342 individuals among woody species::: 10 cm dbh belonging to 169 species grouped into 37 families. The species Gilbertiodendron dewevrei forest characterized monodominant to Gilbertiodendron dewevrei at the upper layer and Coelocaryon preussii and Trichilia spp at the stratum dominated, while the species Petersianthus macrocarpus characterized the old secondary forest at the upper layer and
Trichilia welwitschii Petersianthus macrocarpus and at the stratum dominated. The analysis of ordination (CANOCO software) and classification (PAST software), allowed to differentiate in this reserve at the end of similarities phytosociological surveys, two types of forests: the Forest to monodominant Gilbertiodendron dewevrei and old secondary forest . The species diversity showed a significant difference between these two types of Forest, and also after layer, it appears to II1crease in height decreases in both cases. The human impact that knows this subject at the Forest to monodominant Gilbertiodendron dewevrei is partly responsible for the low density of woody species.