In the light of climate change, it is important to acquire the information on the diversity of flora in order to ensure rational use of steppe rangelands. The present study aimed at diagnosing the botanical and the taxonomic diversity of the arid steppe plant communities in South East of Algeria. A total of 216 phytoecological sampling, were collected in three sites and one sample for each month during 2017 and 2018. The vegetation was analyzed using various species diversity parameters (abundance, species richness, life forms, alpha and beta diversity indices and disturbance index). Results show that 985 plant individuals were classified into 27 species, 27 genera and 14 families, with predominance of Chenopodiaceae and Asteraceae in the arid steppe of El-Haouch, and remarkable dominance of Chamaephytic and Therophytic plants in different phytoecological groups. The state of vegetation degradation in a susceptible environment on Algeria’s rangeland in the South East which is confirmed by the low values of Shannon, Jaccard indices and the values of disturbance index ranged between 50 and 85.71%. The alpha diversity parameters of the different phytoecological groups have low values, which reflect a more fragile homogeneous ecosystem, unfavorable life conditions and the absence of certain species of high pastoral value.