Declared national park since 2003 in the province of Naama in Algeria, it covers an area of around 24,400 hectares. Djebel Aissa national park offers particularly favorables conditions for the development of important floristic diversity with endemic and or rare taxa. The objective of the study is the floristic and ecological characterisation of vegetation in the park. The inventory of the plant biodiversity in study area revealed the existence of 379 taxa belonging to 53 families and 233 genera. An important endemics number has recorded: 24 North Africa, 23 Algerian-Moroccan, 4 North Africa and Iberian Peninsula, 5 Algerian, 6 Saharan, 1 Algerian-Tunisian, 1 ibero-algero-Moroccan and 2 ibero-Moroccan. 65 species were reported as rare or very rare, including 15 quite rare species, 36 rare species, 12 very rare species and 2 extremely rare species. Biological characterisation of species show on clear abundance of therophytes (45%), hemicryptophytes (21%) and chamaephytes (20%).