Though the national Kahuzi-Biega Park be necessarily covered with a forest of well distinguished canopy; it also possesses disturbed areas. This work aims at studying the floristic composition of Ferns and Fern Allies to assess vegetation disturbances in the mountain forests (ranging from 1250 meters to 3000 meters) within the Kahuzi-Biega National Park. Comparisons of vegetation features were made both in disturbed and non-disturbed habitats. Data were collected within 24 plots differently located following the 3 vegetation altitudinal ranges (submontane, montane, afro-alpine) taken into account. In each plot, 4 sampling units of 1ha each were established. Collected data included abundance and dominance features of plant species (both Ferns and their Allies, as well as woody species), tree diameter (DBH), and canopy height, the average of vegetation cover per forest layer (stratum) as well as floristic patterns and species richness. We referred to CANOCO and R (version 2.10.1) softwares to perform our statistical analyses. Results showed that the 3 altitudinal ranges offer differences in their floristic composition. The considered plant features (height, diametric structure) also express variations when disturbed and non-disturbed habitats are taken into consideration. This is for example illustrated by significant differences (results based on a t-test, p-value = 0.007) when one considers the occurrence of Ferns and their Allies. Within stable habitats, Ferns and their Allies particularize themselves by rich and much diversified communities. However, disturbed habitats (following various causes of permanent aggression) face major changes into the floristic composition of their major canopy tree species.