Fennel (Foeniculum vulgare Mill.) is one of the most important, most consuming aromatic and medicinal plants and it is one of the most exportable items in Iran. The fennel has essential oil and seeds are the most important organ that produces essential oil, and the most important compound is anethole (50 to 75). The level and quality of essential oils of fennel are influenced by factors such as different stages of growth and environmental factors (temperature, soil, location, gradient, elevation, and harvest time). The essential oil of this plant is used in various pharmaceutical, food, cosmetic and sanitary industries. The active ingredients of this plant are used in pharmacy for the treatment of cough, abdominal pain, bloating, indigestion in children and increase breast feeding of mothers.