The thymus belongs to the family Lamiaceae, commonly used as spice and medicinal herb, recognized by several pharmacological properties, such as antispasmodic, antiseptic, antibacterial and many other bioactivities. The chemical composition and the antioxidant activity of thymus’s essential oils of three different Moroccan regions were studied. The essential oils were identified by chromatographic analysis (GC and GC/MS). Indeed, in essential oils of Thymus vulgaris and Thymus satureoides the main compound determined was the Carvacrol he represents 78.4% and 49.3% respectively. The quantitative determinations of total phenolics, total flavonoids, and various antioxidant activities (1,1-Diphenyl-l-2-picryl-hydrazyl radical and 2,2-azinobis 3 ethylbenz-thiazoline sulfonate) of plants extracts have carried out using colorimetric methods. The total phenolic content, expressed as μg of gallic acid equivalent (GAE) per mg of extract, was found varied between 121,44 and 143,17 μg GAE/mg and the IC50 values of 1,1-Dipheny l-2-picryl-hydrazyl radical (DPPH) free radical scavenging activity between 5,141 and 5,749 μg/mL. This study indicated the three oils of thymus possessed high antioxidant properties, therefore it can be considered as a bioresource of phenolic and source of natural antioxidant.