Djebel Zdimm is a moutain part of the Tellian high plains (plains located between the coastal Tellian Atlas and the inland pre-Saharan Atlas). Its steppe vegetation has never been scientifically studied. Its location in the semi-arid Tellian high plains gives it a particular character in a territory mainly devoted to cereal cultivation. This mountain is mainly used for grazing. Having a privileged physiognomic setting and exceptional biological context with 243 species, a detailed study was therefore necessary. The inventory of the natural vegetation was carried out to characterize it physiognomically and syntaxonomically while highlighting the importance of environmental conditions and human impacts on vegetation dynamics. This diachronic study demonstrated a trend towards a significant qualitative and quantitative regression of vegetation cover, which decreased by 80% in the most degraded areas. Under the effect of the strong anthropic pressure and climatic hazards, the composition of the steppe vegetation has changed. Species indicating some kind of degradation were : Astragalus armatus, Atractylis serratuloides, Deverra scoparia, Erodium glaucophyllum, Hammada scoparia, Peganum harmala, Tetraena simplex, Thymelaea microphylla.