In Northern Benin, inselberg called Sobakpérou of meridional Sudaneze domain was studied. The objective of this study, concerning only on single site and carried according to the altitudinal gradient, is to describe the plant communities using the phytosociological method. Seven types of plant communities belonging to four plant formations are described: dry deciduous forest, woodland, savanna ... [Show full abstract] and saxicolous grass-plot. On the whole, 172 species belonging to 65 botanical families have been gathered. The most representative families which comprise 28% of species recorded are Poaceae (21 species), Fabaceae (16) and Cyperaceae (12). Plant communities showing a low species diversity are those for which the pH of soil is most acid (4,7 < pH < 5,7). It concerns grass-plot of thin or shallow soil and dry forest living among boulder- falls on the summit of inselberg studied.