Soil genesis is closely related to climatic conditions.The low rainfall reduces the phenomenon of leaching and does in no way fertilization. This work shows that the evolution of soils of the steppe region of Tlemcen is not only the fact of a soil and climate but also the nuances of microstationnels factors (vegetation, slope and altitude). To this end, we found it necessary to make the physical and chemical analyzes combined with a statistical-Principal Component Analysis (PCA) - soils of the steppe region of Tlemcen, to identify characteristics and edaphic see their actions on the distribution and physiognomy of vegetation. Pedogenesis in steppe soils remains our primary concern, for their present condition is a certain imprint on these steppe ecosystems, the limit of their ecological rupture (desertisation).