The vegetation of the central plateau offers strong potential in terms of medicinal plants. In this context, the present research work sets itself the objective of highlighting the flora of the area, first through an ethnobotanical study and then by the choice of three remarkable species of the region (Cistus salviifolius, Cistus Creticus et Lavandula stoechas) in order to submit them for chemical analysis. The ethnobotanical survey, carried out in Oulmes and regions, targets users of traditional medicine, particularly herbalists, the local population and cooperatives working in this field. The plant samples analyzed are collected from the El Harcha forest simultaneously in the number of 3 samples of each plant in three different areas. The results of the ethnobotanical survey showed that most of the species listed are used mainly in the care of the digestive system and the respiratory system. The care is carried out using the whole plant and the infusion represents the most common method of preparation among the local population. Regarding the chemical composition of the above-mentioned plants, it has been demonstrated that they present fractions of macroelements (N, P, K, Ca, Mg) and trace elements which fall within the standards, which shows that the soil of the region is fertile and good for the valorization of plants.