Desertification is a worldwide concern; in Algeria, land degradation threats more than 20 million of steppe rangelands. Protection from grazing is a technique widely used as a management tool for the development of the steppes. The aim of this study is to investigate the effect of grazing on plant community structure and diversity. We conducted a comparative study of the plant community structure and diversity in grazed and ungrazed areas. We assessed soil surface conditions; vegetation, litter, bare ground, biological soil crusts and Stipa tenacissima cover. In addition, we quantified plant species diversity using species richness, Shannon diversity index, Simpson index and Evenness. Our results showed that grazing activities have largely reduced values of the vegetation cover and diversity in grazed areas. In addition, grazing activities affected plant community assemblages. The cover of the most dominant species (Stipa tenacissima), was not affected by grazing. Nevertheless, the protection from grazing increased significantly the species diversity of annual species and vegetation cover. This study highlights the importance of protection and conservation as an effective management tool for maintaining the plant community structure and diversity in threatened ecosystems.