Halocnemum stobilaceum (Chenopodiaceae) is one of many halophyte plants from Algerian Sahara. In this study, we investigate the phytochemical composition and the insecticidal activity of the crude ethanolic extract of this plant against adults of the red flour beetle Tribolium castaneum (Coleoptera: Tenebrionidae). Te effect of this extract on the detoxification enzyme Glutathione S-transferase (GST) and the neuroenzyme Acethylcolinesterase (AChE) was also investigated. The repellent effect was evaluated, at the concentration of 1000 μg/ insect, using the preferential zone method on blotting paper. The insecticidal effect was investigated by testing 5 doses: 100, 200, 400, 800 and 1000 μg/insect. The obtained results show that H. stobilaceum is very rich in saponins, gallic tannins, flavonoids, antocyans, coumarins and alkaloids. The plant is poor in irridoids. On insecticidal level, the extract tested at dose 1000 µg/insecte has a good repellent effect on adults of T. castaneum. The repulsively rate calculated after two hours of exposure was 60%. The extract was toxic too. Indeed, the five tested doses caused mortalities of 15, 33.3, 41.6, 48.3 and 70%, respectively, after 6 hours of exposure. The highest dose (1000 μg/insect) generated 100 deaths after 96 h of exposure. The LD 50 calculated 24 h after treatment was 225.4 μg/insect. Furthermore, the extract of this plant, at the concentration of 1000 µg/insect, inhibited acetylcholinesterase (AChE) activity. The obtained results suggest that extracts of this plant can be used to protect the stored products against insect secondary pest.