This study aims to investigate, the physic-ochemical characterization of Allium sativum, Allium cepa and Foenuculum vulgare. The analysis which carried out on these plants includes pH, titratable acidity, fiber, fat, sugars, soluble solids, pectin and protein. The results from the study of three medicinal plants, show that: Allium sativum, present a low acid vegetable (6.10 ± 0.005), rich in water (63.67% ± 0.1131) and sugars (25.6g / 100g ± 0.034), its pectin content is (2.89 % ± 0.1619) and fiber (1.47% ± 0.007), but contains a low protein content of (0.04mg / ml ± 0.0028) and traces of lipids. Allium cepa had a low acid vegetable (5.42 ± 0.0707), rich in water (92.20% ± 0.0212), sugars (13.16g / 100g ± 0.1416), pectin (3.102% ± 0.0459), and fiber (2.12% ± 0.070). Its protein content (0.1mg / ml ± 0.007) was low, and traces of lipids. For, Foenuculum vulgare, a slightly acidic vegetable (6.02 ± 0.0057), highly rich in water (95.34% ± 0.00), sugars (16.80g / 100g ± 0.1983), dietary fiber (12.20% ± 0, 0785), and pectin (3.79% ± 0.07). However, contains low protein content (0.034mg / ml ± 0.0098), and traces of lipids. The results obtained from this study show that the three plants garlic, onion and fennel have a good chemical composition.