Spearmint (Mentha spicata L.), oregano (Origanum vulgare L.) and thyme (Thymus vulgaris L.) are used as traditional medicines, culinary herbs and food flavorings. All samples collected from Khuzestan province, Iran and plant extracts prepared using Clevenger apparatus. Antioxidant capacity and major parameters affecting antioxidant properties including total phenolics, flavonoids and vitamin C were evaluated using aqueous extract. Chemical composition of essential oil was evaluated be GC/MS analysis. Results showed high antioxidant capacity of thyme (IC50=103.78), followed by spearmint and oregano (IC50 of 143.87 and 164.01 respectively). As previous studies confirmed high correlation of total phenolics, flavonoids and ascorbic acid with antioxidant capacity, thyme had the highest bioactive compounds comparing to other extracts. The highest chemical compounds in thyme, oregano and spearmint were menthol (58.3%), menthol (40.1%) and thymol (39%) respectively. By increasing public interests to natural components, the aim of our study was evaluating antioxidant and bioactive components of plants used locally and try to find and screen new and natural compound for substituting synthetic antioxidant like, BHT.