This work focused on the physicochemical study, phytochemical screening and evaluation of the biological activity of the fruits and leaves of Pistacia atlantica in occidental Algeria (Bechar region).The phytochemical screening shows that this plant is rich in secondary metabolism: flavonoids, tannins, alkaloids, steroids in the leaves we record against lack alkaloids, saponins, steroids and starch and presence of polyphenols in fruit. The performance of the fixed oil of Pistacia atlantica fruit extracted by Soxhlet is around 77%, which is higher compared to the traditional method (3.33%). Leaves result a small amount of 2.2% by the first method. We have used the Disk method to determine the antibacterial activity which was revealed compared to six strains gram positive and gram negative. All tested strains were susceptible against the aqueous extract with an 8mm zone of inhibition, except Pseudomonas aeruginosa given 14mm diameter, fixed oils against the fruit has an antibacterial potency against only grams negative strain.