Essential oil (EO), belonging to the secondary metabolites of plant body, was a kind of liquid of volatile oil with certain special odor that exists in leaves, roots, skins, flowers and fruits of a plant, and can be distilled with water vapor. In this paper, the principles, advantages and disadvantages of traditional extraction methods and new extraction methods of EO were expounded. At the same time, the detection and analysis techniques and the major components of EO were summarized. In addition, the functional characteristics of EO were reviewed. The aim of this article was to provide the references for the follow-up research and development of EO.